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Rückert T, Romagnani C. Extrinsic and intrinsic drivers of natural killer cell clonality. Immunol Rev 2024; 323:80-106. [PMID: 38506411 DOI: 10.1111/imr.13324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
Clonal expansion of antigen-specific lymphocytes is the fundamental mechanism enabling potent adaptive immune responses and the generation of immune memory. Accompanied by pronounced epigenetic remodeling, the massive proliferation of individual cells generates a critical mass of effectors for the control of acute infections, as well as a pool of memory cells protecting against future pathogen encounters. Classically associated with the adaptive immune system, recent work has demonstrated that innate immune memory to human cytomegalovirus (CMV) infection is stably maintained as large clonal expansions of natural killer (NK) cells, raising questions on the mechanisms for clonal selection and expansion in the absence of re-arranged antigen receptors. Here, we discuss clonal NK cell memory in the context of the mechanisms underlying clonal competition of adaptive lymphocytes and propose alternative selection mechanisms that might decide on the clonal success of their innate counterparts. We propose that the integration of external cues with cell-intrinsic sources of heterogeneity, such as variegated receptor expression, transcriptional states, and somatic variants, compose a bottleneck for clonal selection, contributing to the large size of memory NK cell clones.
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Affiliation(s)
- Timo Rückert
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Immunology, Berlin, Germany
| | - Chiara Romagnani
- Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Immunology, Berlin, Germany
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2
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Kravitz SN, Ferris E, Love MI, Thomas A, Quinlan AR, Gregg C. Random allelic expression in the adult human body. Cell Rep 2023; 42:111945. [PMID: 36640362 PMCID: PMC10484211 DOI: 10.1016/j.celrep.2022.111945] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 10/17/2022] [Accepted: 12/15/2022] [Indexed: 01/07/2023] Open
Abstract
Genes are typically assumed to express both parental alleles similarly, yet cell lines show random allelic expression (RAE) for many autosomal genes that could shape genetic effects. Thus, understanding RAE in human tissues could improve our understanding of phenotypic variation. Here, we develop a methodology to perform genome-wide profiling of RAE and biallelic expression in GTEx datasets for 832 people and 54 tissues. We report 2,762 autosomal genes with some RAE properties similar to randomly inactivated X-linked genes. We found that RAE is associated with rapidly evolving regions in the human genome, adaptive signaling processes, and genes linked to age-related diseases such as neurodegeneration and cancer. We define putative mechanistic subtypes of RAE distinguished by gene overlaps on sense and antisense DNA strands, aggregation in clusters near telomeres, and increased regulatory complexity and inputs compared with biallelic genes. We provide foundations to study RAE in human phenotypes, evolution, and disease.
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Affiliation(s)
- Stephanie N Kravitz
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA; Neurobiology, University of Utah, Salt Lake City, UT, USA
| | - Elliott Ferris
- Neurobiology, University of Utah, Salt Lake City, UT, USA
| | - Michael I Love
- Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Alun Thomas
- Department of Internal Medicine, Epidemiology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Aaron R Quinlan
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA
| | - Christopher Gregg
- Department of Human Genetics, University of Utah, Salt Lake City, UT, USA; Neurobiology, University of Utah, Salt Lake City, UT, USA.
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3
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Kubasova N, Alves-Pereira CF, Gupta S, Vinogradova S, Gimelbrant A, Barreto VM. In Vivo Clonal Analysis Reveals Random Monoallelic Expression in Lymphocytes That Traces Back to Hematopoietic Stem Cells. Front Cell Dev Biol 2022; 10:827774. [PMID: 36003148 PMCID: PMC9393635 DOI: 10.3389/fcell.2022.827774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 05/16/2022] [Indexed: 11/24/2022] Open
Abstract
Evaluating the epigenetic landscape in the stem cell compartment at the single-cell level is essential to assess the cells’ heterogeneity and predict their fate. Here, using a genome-wide transcriptomics approach in vivo, we evaluated the allelic expression imbalance in the progeny of single hematopoietic cells (HSCs) as a read-out of epigenetic marking. After 4 months of extensive proliferation and differentiation, we found that X-chromosome inactivation (XCI) is tightly maintained in all single-HSC derived hematopoietic cells. In contrast, the vast majority of the autosomal genes did not show clonal patterns of random monoallelic expression (RME). However, a persistent allele-specific autosomal transcription in HSCs and their progeny was found in a rare number of cases, none of which has been previously reported. These data show that: 1) XCI and RME in the autosomal chromosomes are driven by different mechanisms; 2) the previously reported high frequency of genes under RME in clones expanded in vitro (up to 15%) is not found in clones undergoing multiple differentiation steps in vivo; 3) prior to differentiation, HSCs have stable patterns of autosomal RME. We propose that most RME patterns in autosomal chromosomes are erased and established de novo during cell lineage differentiation.
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Affiliation(s)
- Nadiya Kubasova
- Chronic Diseases Research Centre, Nova Medical School, CEDOC, Lisbon, Portugal
- Genetagus, Egas Moniz – Cooperativa de Ensino Superior, CRL, Monte de Caparica, Portugal
| | - Clara F. Alves-Pereira
- Center of Cancer Systems Biology, Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, United States
- Department of Genetics, Harvard Medical School, Boston, MA, United States
- Broad Institute of MIT and Harvard, Cambridge, MA, United States
- Department of Genetics, Smurfit Institute of Genetics, Trinity College Dublin, University of Dublin, Dublin, Ireland
| | - Saumya Gupta
- Center of Cancer Systems Biology, Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, United States
- Department of Genetics, Harvard Medical School, Boston, MA, United States
- Broad Institute of MIT and Harvard, Cambridge, MA, United States
| | - Svetlana Vinogradova
- Center of Cancer Systems Biology, Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, United States
- Department of Genetics, Harvard Medical School, Boston, MA, United States
- Broad Institute of MIT and Harvard, Cambridge, MA, United States
| | - Alexander Gimelbrant
- Center of Cancer Systems Biology, Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, United States
- Department of Genetics, Harvard Medical School, Boston, MA, United States
- Broad Institute of MIT and Harvard, Cambridge, MA, United States
- *Correspondence: Vasco M. Barreto, ; Alexander Gimelbrant,
| | - Vasco M. Barreto
- Chronic Diseases Research Centre, Nova Medical School, CEDOC, Lisbon, Portugal
- UCIBIO, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Costa da Caparica, Portugal
- *Correspondence: Vasco M. Barreto, ; Alexander Gimelbrant,
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Abstract
Monoallelic expression (MAE) or extreme allele bias can account for incomplete penetrance, missing heritability and non-Mendelian diseases. In cancer, MAE is associated with shorter patient survival times and higher tumor grade. Prior studies showed that stochastic MAE is caused by stochastic epigenetic silencing, in a gene and tissue-specific manner. Here, we used C. elegans to study stochastic MAE in vivo. We found allele bias/MAE to be widespread within C. elegans tissues, presenting as a continuum from fully biallelic to MAE. We discovered that the presence of introns within alleles robustly decreases MAE. We determined that introns control MAE at distinct loci, in distinct cell types, with distinct promoters, and within distinct coding sequences, using a 5'-intron position-dependent mechanism. Bioinformatic analysis showed human intronless genes are significantly enriched for MAE. Our experimental evidence demonstrates a role for introns in regulating MAE, possibly explaining why some mutations within introns result in disease.
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Affiliation(s)
- Bryan Sands
- grid.34477.330000000122986657Department of Laboratory Medicine and Pathology, School of Medicine, University of Washington, Seattle, WA USA
| | - Soo Yun
- grid.34477.330000000122986657Department of Laboratory Medicine and Pathology, School of Medicine, University of Washington, Seattle, WA USA
| | - Alexander R. Mendenhall
- grid.34477.330000000122986657Department of Laboratory Medicine and Pathology, School of Medicine, University of Washington, Seattle, WA USA
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5
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Marion-Poll L, Forêt B, Zielinski D, Massip F, Attia M, Carter AC, Syx L, Chang HY, Gendrel AV, Heard E. Locus specific epigenetic modalities of random allelic expression imbalance. Nat Commun 2021; 12:5330. [PMID: 34504093 PMCID: PMC8429725 DOI: 10.1038/s41467-021-25630-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 08/19/2021] [Indexed: 01/02/2023] Open
Abstract
Most autosomal genes are thought to be expressed from both alleles, with some notable exceptions, including imprinted genes and genes showing random monoallelic expression (RME). The extent and nature of RME has been the subject of debate. Here we investigate the expression of several candidate RME genes in F1 hybrid mouse cells before and after differentiation, to define how they become persistently, monoallelically expressed. Clonal monoallelic expression is not present in embryonic stem cells, but we observe high frequencies of monoallelism in neuronal progenitor cells by assessing expression status in more than 200 clones. We uncover unforeseen modes of allelic expression that appear to be gene-specific and epigenetically regulated. This non-canonical allelic regulation has important implications for development and disease, including autosomal dominant disorders and opens up therapeutic perspectives.
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Affiliation(s)
- Lucile Marion-Poll
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France.
- Directors' research, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
| | - Benjamin Forêt
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France
| | - Dina Zielinski
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France
- Institut Curie, PSL Research University, INSERM U900, Mines ParisTech, Paris, France
| | - Florian Massip
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Mikael Attia
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France
| | - Ava C Carter
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, CA, USA
| | - Laurène Syx
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France
- Institut Curie, PSL Research University, INSERM U900, Mines ParisTech, Paris, France
| | - Howard Y Chang
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, CA, USA
| | - Anne-Valerie Gendrel
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France.
| | - Edith Heard
- Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, Paris, France.
- Directors' research, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
- Collège de France, Paris, France.
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6
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Abstract
Diploidy has profound implications for population genetics and susceptibility to genetic diseases. Although two copies are present for most genes in the human genome, they are not necessarily both active or active at the same level in a given individual. Genomic imprinting, resulting in exclusive or biased expression in favor of the allele of paternal or maternal origin, is now believed to affect hundreds of human genes. A far greater number of genes display unequal expression of gene copies due to cis-acting genetic variants that perturb gene expression. The availability of data generated by RNA sequencing applied to large numbers of individuals and tissue types has generated unprecedented opportunities to assess the contribution of genetic variation to allelic imbalance in gene expression. Here we review the insights gained through the analysis of these data about the extent of the genetic contribution to allelic expression imbalance, the tools and statistical models for gene expression imbalance, and what the results obtained reveal about the contribution of genetic variants that alter gene expression to complex human diseases and phenotypes.
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Affiliation(s)
- Siobhan Cleary
- School of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway H91 H3CY, Ireland;
| | - Cathal Seoighe
- School of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway H91 H3CY, Ireland;
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7
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Dini P, Kalbfleisch T, Uribe-Salazar JM, Carossino M, Ali HES, Loux SC, Esteller-Vico A, Norris JK, Anand L, Scoggin KE, Rodriguez Lopez CM, Breen J, Bailey E, Daels P, Ball BA. Parental bias in expression and interaction of genes in the equine placenta. Proc Natl Acad Sci U S A 2021; 118:e2006474118. [PMID: 33853939 PMCID: PMC8072238 DOI: 10.1073/pnas.2006474118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Most autosomal genes in the placenta show a biallelic expression pattern. However, some genes exhibit allele-specific transcription depending on the parental origin of the chromosomes on which the copy of the gene resides. Parentally expressed genes are involved in the reciprocal interaction between maternal and paternal genes, coordinating the allocation of resources between fetus and mother. One of the main challenges of studying parental-specific allelic expression (allele-specific expression [ASE]) in the placenta is the maternal cellular remnant at the fetomaternal interface. Horses (Equus caballus) have an epitheliochorial placenta in which both the endometrial epithelium and the epithelium of the chorionic villi are juxtaposed with minimal extension into the uterine mucosa, yet there is no information available on the allelic gene expression of equine chorioallantois (CA). In the current study, we present a dataset of 1,336 genes showing ASE in the equine CA (https://pouya-dini.github.io/equine-gene-db/) along with a workflow for analyzing ASE genes. We further identified 254 potentially imprinted genes among the parentally expressed genes in the equine CA and evaluated the expression pattern of these genes throughout gestation. Our gene ontology analysis implies that maternally expressed genes tend to decrease the length of gestation, while paternally expressed genes extend the length of gestation. This study provides fundamental information regarding parental gene expression during equine pregnancy, a species with a negligible amount of maternal cellular remnant in its placenta. This information will provide the basis for a better understanding of the role of parental gene expression in the placenta during gestation.
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Affiliation(s)
- Pouya Dini
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
- Department of Veterinary Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Merelbeke 9820, Belgium
| | - Theodore Kalbfleisch
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40202
| | - José M Uribe-Salazar
- Department of Biochemistry and Molecular Medicine, Genome Center, Medical Investigation of Neurodevelopmental Disorders Institute, University of California, Davis, CA 95616
| | - Mariano Carossino
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Hossam El-Sheikh Ali
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
- Theriogenology Department, Faculty of Veterinary Medicine, University of Mansoura, 35516, Egypt
| | - Shavahn C Loux
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Alejandro Esteller-Vico
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Jamie K Norris
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Lakshay Anand
- Environmental Epigenetics and Genetics Group, Department of Horticulture, University of Kentucky, Lexington, KY 40546
| | - Kirsten E Scoggin
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Carlos M Rodriguez Lopez
- Environmental Epigenetics and Genetics Group, Department of Horticulture, University of Kentucky, Lexington, KY 40546
| | - James Breen
- South Australian Health and Medical Research Institute, Adelaide, SA 5001, Australia
| | - Ernest Bailey
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503
| | - Peter Daels
- Department of Veterinary Medical Imaging and Small Animal Orthopaedics, Faculty of Veterinary Medicine, Ghent University, Merelbeke 9820, Belgium
| | - Barry A Ball
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40503;
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8
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Rv P, Sundaresh A, Karunyaa M, Arun A, Gayen S. Autosomal Clonal Monoallelic Expression: Natural or Artifactual? Trends Genet 2020; 37:206-211. [PMID: 33234351 DOI: 10.1016/j.tig.2020.10.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 01/08/2023]
Abstract
The prevalence of mitotically heritable clonal random monoallelic expression of autosomal genes (aRME) remains controversial. Specifically, presence of clonal aRME is well supported in vitro but remains elusive in vivo. Here, we provide critical insights into this matter and discuss whether prevalent clonal aRME is natural or artifactual.
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Affiliation(s)
- P Rv
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India
| | - A Sundaresh
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India
| | - M Karunyaa
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India
| | - A Arun
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India
| | - S Gayen
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India.
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9
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Kravitz SN, Gregg C. New subtypes of allele-specific epigenetic effects: implications for brain development, function and disease. Curr Opin Neurobiol 2019; 59:69-78. [PMID: 31153086 DOI: 10.1016/j.conb.2019.04.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 04/24/2019] [Indexed: 01/15/2023]
Abstract
Typically, it is assumed that the maternal and paternal alleles for most genes are equally expressed. Known exceptions include canonical imprinted genes, random X-chromosome inactivation, olfactory receptors and clustered protocadherins. Here, we highlight recent studies showing that allele-specific expression is frequent in the genome and involves subtypes of epigenetic allelic effects that differ in terms of heritability, clonality and stability over time. Different forms of epigenetic allele regulation could have different roles in brain development, function, and disease. An emerging area involves understanding allelic effects in a cell-type and developmental stage-specific manner and determining how these effects influence the impact of genetic variants and mutations on the brain. A deeper understanding of epigenetics at the allele and cellular level in the brain could help clarify the mechanisms underlying phenotypic variance.
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Affiliation(s)
- Stephanie N Kravitz
- Department of Neurobiology & Anatomy, University of Utah, Salt Lake City, UT 84132-3401, USA; Department of Human Genetics, University of Utah, Salt Lake City, UT 84132-3401, USA
| | - Christopher Gregg
- Department of Neurobiology & Anatomy, University of Utah, Salt Lake City, UT 84132-3401, USA; Department of Human Genetics, University of Utah, Salt Lake City, UT 84132-3401, USA.
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10
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van der Veeken J, Zhong Y, Sharma R, Mazutis L, Dao P, Pe'er D, Leslie CS, Rudensky AY. Natural Genetic Variation Reveals Key Features of Epigenetic and Transcriptional Memory in Virus-Specific CD8 T Cells. Immunity 2019; 50:1202-1217.e7. [PMID: 31027997 DOI: 10.1016/j.immuni.2019.03.031] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 01/15/2019] [Accepted: 03/27/2019] [Indexed: 12/29/2022]
Abstract
Stable changes in chromatin states and gene expression in cells of the immune system form the basis for memory of infections and other challenges. Here, we used naturally occurring cis-regulatory variation in wild-derived inbred mouse strains to explore the mechanisms underlying long-lasting versus transient gene regulation in CD8 T cells responding to acute viral infection. Stably responsive DNA elements were characterized by dramatic and congruent chromatin remodeling events affecting multiple neighboring sites and required distinct transcription factor (TF) binding motifs for their accessibility. Specifically, we found that cooperative recruitment of T-box and Runx family transcription factors to shared targets mediated stable chromatin remodeling upon T cell activation. Our observations provide insights into the molecular mechanisms driving virus-specific CD8 T cell responses and suggest a general mechanism for the formation of transcriptional and epigenetic memory applicable to other immune and non-immune cells.
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Affiliation(s)
- Joris van der Veeken
- Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Ludwig Center at Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Yi Zhong
- Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Ludwig Center at Memorial Sloan Kettering Cancer Center, New York, NY, USA; Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Roshan Sharma
- Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
| | - Linas Mazutis
- Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Phuong Dao
- Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Dana Pe'er
- Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Christina S Leslie
- Computational and Systems Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Alexander Y Rudensky
- Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Ludwig Center at Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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11
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Symmons O, Chang M, Mellis IA, Kalish JM, Park J, Suszták K, Bartolomei MS, Raj A. Allele-specific RNA imaging shows that allelic imbalances can arise in tissues through transcriptional bursting. PLoS Genet 2019; 15:e1007874. [PMID: 30625149 DOI: 10.1371/journal.pgen.1007874] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/22/2019] [Accepted: 12/04/2018] [Indexed: 12/03/2022] Open
Abstract
Extensive cell-to-cell variation exists even among putatively identical cells, and there is great interest in understanding how the properties of transcription relate to this heterogeneity. Differential expression from the two gene copies in diploid cells could potentially contribute, yet our ability to measure from which gene copy individual RNAs originated remains limited, particularly in the context of tissues. Here, we demonstrate quantitative, single molecule allele-specific RNA FISH adapted for use on tissue sections, allowing us to determine the chromosome of origin of individual RNA molecules in formaldehyde-fixed tissues. We used this method to visualize the allele-specific expression of Xist and multiple autosomal genes in mouse kidney. By combining these data with mathematical modeling, we evaluated models for allele-specific heterogeneity, in particular demonstrating that apparent expression from only one of the alleles in single cells can arise as a consequence of low-level mRNA abundance and transcriptional bursting. In mammals, most cells of the body contain two genetic datasets: one from the mother and one from the father, and—in theory—these two sets of information could contribute equally to produce the molecules in a given cell. In practice, however, this is not always the case, which can have dramatic implications for many traits, including visible features (such as fur color) and even disease outcomes. However, it remains difficult to measure the parental origin of individual molecules in a given cell and thus to assess what processes lead to an imbalance of the maternal and paternal contribution. We adapted a microscopy technique—called allele-specific single molecule RNA FISH—that uses a combination of fluorescent tags to specifically label one type of molecule, RNA, depending on its origin, for use in mouse kidney sections. Focusing on RNAs that were previously reported to show imbalance, we performed measurements and combined these with mathematical modeling to quantify imbalance in tissues and explain how these can arise. We found that we could recapitulate the observed imbalances using models that only take into account the random processes that produce RNA, without the need to invoke special regulatory mechanisms to create unequal contributions.
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