Publications by authors named "Mikael Sigvardsson"

113 Publications

The transcriptional repressor ID2 supports natural killer cell maturation by controlling TCF1 amplitude.

J Exp Med 2021 Jun;218(6)

Department of Pathology, Committees on Immunology and Cancer Biology, The University of Chicago, Chicago, IL.

Gaining a mechanistic understanding of the expansion and maturation program of natural killer (NK) cells will provide opportunities for harnessing their inflammation-inducing and oncolytic capacity for therapeutic purposes. Here, we demonstrated that ID2, a transcriptional regulatory protein constitutively expressed in NK cells, supports NK cell effector maturation by controlling the amplitude and temporal dynamics of the transcription factor TCF1. TCF1 promotes immature NK cell expansion and restrains differentiation. The increased TCF1 expression in ID2-deficient NK cells arrests their maturation and alters cell surface receptor expression. Moreover, TCF1 limits NK cell functions, such as cytokine-induced IFN-γ production and the ability to clear metastatic melanoma in ID2-deficient NK cells. Our data demonstrate that ID2 sets a threshold for TCF1 during NK cell development, thus controlling the balance of immature and terminally differentiated cells that support future NK cell responses.
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http://dx.doi.org/10.1084/jem.20202032DOI Listing
June 2021

EBF1 and PAX5 control pro-B cell expansion via opposing regulation of the Myc gene.

Blood 2021 Feb 22. Epub 2021 Feb 22.

Lund University, Sweden.

Genes encoding B lineage restricted transcription factors are frequently mutated in B-lymphoid leukemias, suggesting a close link between normal and malignant B-cell development. One of these transcription factors is Early B cell Factor 1 (EBF1), a protein of critical importance for lineage specification and survival of B-lymphoid progenitors. Here, we report that impaired EBF1 function in mouse B-cell progenitors results in reduced expression of Myc. Ectopic expression of MYC partially rescued B-cell expansion in the absence of EBF1 both in vivo and in vitro. Using chromosome conformation analysis in combination with ATAC-seq, ChIP-seq and reporter gene assays, we identified six EBF responsive enhancer elements within the Myc locus. CRISPR-Cas9 mediated targeting of EBF1 binding sites identified one element of key importance for Myc expression and pro-B cell expansion. These data provide evidence that Myc is a direct target of EBF1. Furthermore, ChIP-seq analysis revealed that several regulatory elements in the Myc locus are targets of PAX5. However, ectopic expression of PAX5 in EBF1 deficient cells inhibits the cell cycle and reduces Myc expression, suggesting that EBF1 and PAX5 act in an opposing manner to regulate Myc levels. This hypothesis is further substantiated by the finding that Pax5 inactivation reduces requirements for EBF1 in pro-B cell expansion. The binding of EBF1 and PAX5 to regulatory elements in the human MYC gene in a B-ALL cell line indicate that the EBF1:PAX5:MYC regulatory loop is conserved and may control both normal and malignant B-cell development.
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http://dx.doi.org/10.1182/blood.2020009564DOI Listing
February 2021

Prospective isolation of radiation induced erythroid stress progenitors reveals unique transcriptomic and epigenetic signatures enabling increased erythroid output.

Haematologica 2020 11 1;105(11):2561-2571. Epub 2020 Nov 1.

Division of Molecular Medicine and Gene Therapy, Lund Stem Cell Center, Lund University, Sweden.

Massive expansion of erythroid progenitor cells is essential for surviving anemic stress. Research towards understanding this critical process, referred to as stress-erythropoiesis, has been hampered due to lack of specific marker-combinations enabling analysis of the distinct stress-progenitor cells capable of providing radioprotection and enhanced red blood cell production. Here we present a method for precise identification and in vivo validation of progenitor cells contributing to both steady-state and stress-erythropoiesis, enabling for the first time in-depth molecular characterization of these cells. Differential expression of surface markers CD150, CD9 and Sca1 defines a hierarchy of splenic stress-progenitors during irradiation-induced stress recovery in mice, and provides high-purity isolation of the functional stress-BFU-Es with a 100-fold improved enrichment compared to state-of-the-art. By transplanting purified stress-progenitors expressing the fluorescent protein Kusabira Orange, we determined their kinetics in vivo and demonstrated that CD150+CD9+Sca1- stress-BFU-Es provide a massive but transient radioprotective erythroid wave, followed by multi-lineage reconstitution from CD150+CD9+Sca1+ multi-potent stem/progenitor cells. Whole genome transcriptional analysis revealed that stress-BFU-Es express gene signatures more associated with erythropoiesis and proliferation compared to steady-state BFU-Es, and are BMP-responsive. Evaluation of chromatin accessibility through ATAC sequencing reveals enhanced and differential accessibility to binding sites of the chromatin-looping transcription factor CTCF in stress-BFU-Es compared to steady-state BFU-Es. Our findings offer molecular insight to the unique capacity of stress-BFU-Es to rapidly form erythroid cells in response to anemia and constitute an important step towards identifying novel erythropoiesis stimulating agents.
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http://dx.doi.org/10.3324/haematol.2019.234542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7604643PMC
November 2020

ARID1a Associates with Lymphoid-Restricted Transcription Factors and Has an Essential Role in T Cell Development.

J Immunol 2020 09 3;205(5):1419-1432. Epub 2020 Aug 3.

Department of Biomedical and Clinical Sciences, Linköping University, 581 85 Linköping, Sweden.

Maturation of lymphoid cells is controlled by the action of stage and lineage-restricted transcription factors working in concert with the general transcription and chromatin remodeling machinery to regulate gene expression. To better understand this functional interplay, we used Biotin Identification in human embryonic kidney cells to identify proximity interaction partners for GATA3, TCF7 (TCF1), SPI1, HLF, IKZF1, PAX5, ID1, and ID2. The proximity interaction partners shared among the lineage-restricted transcription factors included ARID1a, a BRG1-associated factor complex component. CUT&RUN analysis revealed that ARID1a shared binding with TCF7 and GATA3 at a substantial number of putative regulatory elements in mouse T cell progenitors. In support of an important function for ARID1a in lymphocyte development, deletion of in early lymphoid progenitors in mice resulted in a pronounced developmental arrest in early T cell development with a reduction of CD4CD8 cells and a 20-fold reduction in thymic cellularity. Exploring gene expression patterns in DN3 cells from and -deficient mice suggested that the developmental block resided in the DN3a to DN3b transition, indicating a deficiency in β-selection. Our work highlights the critical importance of functional interactions between stage and lineage-restricted factors and the basic transcription machinery during lymphocyte differentiation.
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http://dx.doi.org/10.4049/jimmunol.1900959DOI Listing
September 2020

The transcription factor BCL-6 controls early development of innate-like T cells.

Nat Immunol 2020 09 27;21(9):1058-1069. Epub 2020 Jul 27.

Institute for Fundamental Biomedical Research, BSRC Alexander Fleming, Vari, Greece.

Innate T cells, including invariant natural killer T (iNKT) and mucosal-associated innate T (MAIT) cells, are a heterogeneous T lymphocyte population with effector properties preprogrammed during their thymic differentiation. How this program is initiated is currently unclear. Here, we show that the transcription factor BCL-6 was transiently expressed in iNKT cells upon exit from positive selection and was required for their proper development beyond stage 0. Notably, development of MAIT cells was also impaired in the absence of Bcl6. BCL-6-deficient iNKT cells had reduced expression of genes that were associated with the innate T cell lineage, including Zbtb16, which encodes PLZF, and PLZF-targeted genes. BCL-6 contributed to a chromatin accessibility landscape that was permissive for the expression of development-related genes and inhibitory for genes associated with naive T cell programs. Our results revealed new functions for BCL-6 and illuminated how this transcription factor controls early iNKT cell development.
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http://dx.doi.org/10.1038/s41590-020-0737-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442690PMC
September 2020

13q12.2 deletions in acute lymphoblastic leukemia lead to upregulation of FLT3 through enhancer hijacking.

Blood 2020 08;136(8):946-956

Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, Lund, Sweden.

Mutations in the FMS-like tyrosine kinase 3 (FLT3) gene in 13q12.2 are among the most common driver events in acute leukemia, leading to increased cell proliferation and survival through activation of the phosphatidylinositol 3-kinase/AKT-, RAS/MAPK-, and STAT5-signaling pathways. In this study, we examine the pathogenetic impact of somatic hemizygous 13q12.2 microdeletions in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) using 5 different patient cohorts (in total including 1418 cases). The 13q12.2 deletions occur immediately 5' of FLT3 and involve the PAN3 locus. By detailed analysis of the 13q12.2 segment, we show that the deletions lead to loss of a topologically associating domain border and an enhancer of FLT3. This results in increased cis interactions between the FLT3 promoter and another enhancer located distally to the deletion breakpoints, with subsequent allele-specific upregulation of FLT3 expression, expected to lead to ligand-independent activation of the receptor and downstream signaling. The 13q12.2 deletions are highly enriched in the high-hyperdiploid BCP ALL subtype (frequency 3.9% vs 0.5% in other BCP ALL) and in cases that subsequently relapsed. Taken together, our study describes a novel mechanism of FLT3 involvement in leukemogenesis by upregulation via chromatin remodeling and enhancer hijacking. These data further emphasize the role of FLT3 as a driver gene in BCP ALL.
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http://dx.doi.org/10.1182/blood.2019004684DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498303PMC
August 2020

Ezh2 Represses Transcription of Innate Lymphoid Genes in B Lymphocyte Progenitors and Maintains the B-2 Cell Fate.

J Immunol 2020 04 24;204(7):1760-1769. Epub 2020 Feb 24.

Committee on Immunology, The University of Chicago, Chicago, IL 60657;

Lymphocyte lineage specification and commitment requires the activation of lineage-specific genes and repression of alternative lineage genes, respectively. The mechanisms governing alternative lineage gene repression and commitment in lymphocytes are largely unknown. In this study, we demonstrate that Ezh2, which represses gene expression through methylation of histone 3 lysine 27, was essential for repression of numerous genes, including genes encoding innate lymphocyte transcription factors, specifically in murine B lymphocyte progenitors, but these cells maintained their B lymphocyte identity. However, adult Ezh2-deficient B lymphocytes expressed , which encodes an RNA-binding protein associated with fetal hematopoietic gene expression programs, and these cells acquired a fetal B-1 lymphocyte phenotype in vitro and in vivo. Therefore, Ezh2 coordinates the repression of multiple gene programs in B lymphocytes and maintains the adult B-2 cell fate.
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http://dx.doi.org/10.4049/jimmunol.1901188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7344269PMC
April 2020

Lin28b controls a neonatal to adult switch in B cell positive selection.

Sci Immunol 2019 09;4(39)

Developmental Immunology Unit, Division of Molecular Hematology, Department of Laboratory Medicine, Lund Stem Cell Center, Lund University, 22242 Lund, Sweden.

The ability of B-1 cells to become positively selected into the mature B cell pool, despite being weakly self-reactive, has puzzled the field since its initial discovery. Here, we explore changes in B cell positive selection as a function of developmental time by exploiting a link between CD5 surface levels and the natural occurrence of self-reactive B cell receptors (BCRs) in BCR wild-type mice. We show that the heterochronic RNA binding protein Lin28b potentiates a neonatal mode of B cell selection characterized by enhanced overall positive selection in general and the developmental progression of CD5 immature B cells in particular. Lin28b achieves this by amplifying the CD19/PI3K/c-Myc positive feedback loop, and ectopic Lin28b expression restores both positive selection and mature B cell numbers in CD19 adult mice. Thus, the temporally restricted expression of relaxes the rules for B cell selection during ontogeny by modulating tonic signaling. We propose that this neonatal mode of B cell selection represents a cell-intrinsic cue to accelerate the de novo establishment of the adaptive immune system and incorporate a layer of natural antibody-mediated immunity throughout life.
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http://dx.doi.org/10.1126/sciimmunol.aax4453DOI Listing
September 2019

PAX5 is part of a functional transcription factor network targeted in lymphoid leukemia.

PLoS Genet 2019 08 5;15(8):e1008280. Epub 2019 Aug 5.

Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.

One of the most frequently mutated proteins in human B-lineage leukemia is the transcription factor PAX5. These mutations often result in partial rather than complete loss of function of the transcription factor. While the functional dose of PAX5 has a clear connection to human malignancy, there is limited evidence for that heterozygote loss of PAX5 have a dramatic effect on the development and function of B-cell progenitors. One possible explanation comes from the finding that PAX5 mutated B-ALL often display complex karyotypes and additional mutations. Thus, PAX5 might be one component of a larger transcription factor network targeted in B-ALL. To investigate the functional network associated with PAX5 we used BioID technology to isolate proteins associated with this transcription factor in the living cell. This identified 239 proteins out of which several could be found mutated in human B-ALL. Most prominently we identified the commonly mutated IKZF1 and RUNX1, involved in the formation of ETV6-AML1 fusion protein, among the interaction partners. ChIP- as well as PLAC-seq analysis supported the idea that these factors share a multitude of target genes in human B-ALL cells. Gene expression analysis of mouse models and primary human leukemia suggested that reduced function of PAX5 increased the ability of an oncogenic form of IKZF1 or ETV6-AML to modulate gene expression. Our data reveals that PAX5 belong to a regulatory network frequently targeted by multiple mutations in B-ALL shedding light on the molecular interplay in leukemia cells.
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http://dx.doi.org/10.1371/journal.pgen.1008280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6695195PMC
August 2019

Cutting Edge: Lymphomyeloid-Primed Progenitor Cell Fates Are Controlled by the Transcription Factor Tal1.

J Immunol 2019 05 8;202(10):2837-2842. Epub 2019 Apr 8.

Department of Pathology, The University of Chicago, Chicago, IL 60637;

Lymphoid specification is the process by which hematopoietic stem cells (HSCs) and their progeny become restricted to differentiation through the lymphoid lineages. The basic helix-loop-helix transcription factors E2A and Lyl1 form a complex that promotes lymphoid specification. In this study, we demonstrate that Tal1, a Lyl1-related basic helix-loop-helix transcription factor that promotes T acute lymphoblastic leukemia and is required for HSC specification, erythropoiesis, and megakaryopoiesis, is a negative regulator of murine lymphoid specification. We demonstrate that Tal1 limits the expression of multiple E2A target genes in HSCs and controls the balance of myeloid versus T lymphocyte differentiation potential in lymphomyeloid-primed progenitors. Our data provide insight into the mechanisms controlling lymphocyte specification and may reveal a basis for the unique functions of Tal1 and Lyl1 in T acute lymphoblastic leukemia.
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http://dx.doi.org/10.4049/jimmunol.1801220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6504590PMC
May 2019

Pioneering, chromatin remodeling, and epigenetic constraint in early T-cell gene regulation by SPI1 (PU.1).

Genome Res 2018 10 31;28(10):1508-1519. Epub 2018 Aug 31.

Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA.

SPI1 (also known as PU.1) is a dominant but transient regulator in early T-cell precursors and a potent transcriptional controller of developmentally important pro-T-cell genes. Before T-lineage commitment, open chromatin is frequently occupied by PU.1, and many PU.1 sites lose accessibility when PU.1 is later down-regulated. Pioneering activity of PU.1 was tested in this developmentally dynamic context by quantitating the relationships between PU.1 occupancy and site quality and accessibility as PU.1 levels naturally declined in pro-T-cell development and by using stage-specific gain- and loss-of-function perturbations to relate binding to effects on target genes. PU.1 could bind closed genomic sites, but rapidly opened many of them, despite the absence of its frequent collaborator, CEBPA. RUNX motifs and RUNX1 binding were often linked to PU.1 at open sites, but highly expressed PU.1 could bind its sites without RUNX1. The dynamic properties of PU.1 engagements implied that PU.1 binding affinity and concentration determine its occupancy choices, but with quantitative trade-offs for occupancy between site sequence quality and stage-dependent site accessibility in chromatin. At nonpromoter sites, PU.1 binding criteria were more stringent than at promoters, and PU.1 was also much more effective as a transcriptional regulator at nonpromoter sites where local chromatin accessibility depended on the presence of PU.1. Notably, closed chromatin presented a qualitative barrier to occupancy by the PU.1 DNA-binding domain alone. Thus, effective pioneering at closed chromatin sites also depends on requirements beyond site recognition, served by non-DNA-binding domains of PU.1.
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http://dx.doi.org/10.1101/gr.231423.117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6169891PMC
October 2018

Molecular Regulation of Differentiation in Early B-Lymphocyte Development.

Int J Mol Sci 2018 Jun 30;19(7). Epub 2018 Jun 30.

Division of Molecular Hematology, Lund Stem Cell Center, Department of Laboratory Medicine, Lund University, 22184 Lund, Sweden.

B-lymphocyte differentiation is one of the best understood developmental pathways in the hematopoietic system. Our understanding of the developmental trajectories linking the multipotent hematopoietic stem cell to the mature functional B-lymphocyte is extensive as a result of efforts to identify and prospectively isolate progenitors at defined maturation stages. The identification of defined progenitor compartments has been instrumental for the resolution of the molecular features that defines given developmental stages as well as for our understanding of the mechanisms that drive the progressive maturation process. Over the last years it has become increasingly clear that the regulatory networks that control normal B-cell differentiation are targeted by mutations in human B-lineage malignancies. This generates a most interesting link between development and disease that can be explored to improve diagnosis and treatment protocols in lymphoid malignancies. The aim of this review is to provide an overview of our current understanding of molecular regulation in normal and malignant B-cell development.
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http://dx.doi.org/10.3390/ijms19071928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073616PMC
June 2018

Distinct roles of mesenchymal stem and progenitor cells during the development of acute myeloid leukemia in mice.

Blood Adv 2018 06;2(12):1480-1494

Center for Hematology and Regenerative Medicine, Department of Medicine, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden.

Despite increasing evidence for the involvement of bone marrow (BM) hematopoietic stem cell niche in leukemogenesis, how BM mesenchymal stem and progenitor cells (MSPCs) contribute to leukemia niche formation and progression remains unclear. Using an MLL-AF9 acute myeloid leukemia (AML) mouse model, we demonstrate dynamic alterations of BM cellular niche components, including MSPCs and endothelial cells during AML development and its association with AML engraftment. Primary patient AML cells also induced similar niche alterations in xenografted mice. AML cell infiltration in BM causes an expansion of early B-cell factor 2 (Ebf2) MSPCs with reduced expression and enhanced generation of more differentiated mesenchymal progenitor cells. Importantly, in vivo fate-mapping indicates that Ebf2 MSPCs participated in AML niche formation. Ebf2 cell deletion accelerated the AML development. These data suggest that native BM MSPCs may suppress AML. However, they can be remodeled by AML cells to form leukemic niche that might contribute to AML progression. AML induced dysregulation of hematopoietic niche factors like , , , , , and in AML BM MSPCs, which was associated with AML engraftment and partially appeared before the massive expansion of AML cells, indicating the possible involvement of the niche factors in AML progression. Our study demonstrates distinct dynamic features and roles of BM MSPCs during AML development.
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http://dx.doi.org/10.1182/bloodadvances.2017013870DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6020803PMC
June 2018

Zinc Finger Protein 521 Regulates Early Hematopoiesis through Cell-Extrinsic Mechanisms in the Bone Marrow Microenvironment.

Mol Cell Biol 2018 09 15;38(17). Epub 2018 Aug 15.

Department of Biomedical Sciences, National Jewish Health, Denver, Colorado, USA

Zinc finger protein 521 (ZFP521), a DNA-binding protein containing 30 Krüppel-like zinc fingers, has been implicated in the differentiation of multiple cell types, including hematopoietic stem and progenitor cells (HSPC) and B lymphocytes. Here, we report a novel role for ZFP521 in regulating the earliest stages of hematopoiesis and lymphoid cell development via a cell-extrinsic mechanism. Mice with inactivated genes () possess reduced frequencies and numbers of hematopoietic stem and progenitor cells, common lymphoid progenitors, and B and T cell precursors. Notably, ZFP521 deficiency changes bone marrow microenvironment cytokine levels and gene expression within resident HSPC, consistent with a skewing of hematopoiesis away from lymphopoiesis. These results advance our understanding of ZFP521's role in normal hematopoiesis, justifying further research to assess its potential as a target for cancer therapies.
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http://dx.doi.org/10.1128/MCB.00603-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6094055PMC
September 2018

Dissection of progenitor compartments resolves developmental trajectories in B-lymphopoiesis.

J Exp Med 2018 07 13;215(7):1947-1963. Epub 2018 Jun 13.

Division of Molecular Hematology, Lund University, Lund, Sweden

To understand the developmental trajectories in early lymphocyte differentiation, we identified differentially expressed surface markers on lineage-negative lymphoid progenitors (LPs). Single-cell polymerase chain reaction experiments allowed us to link surface marker expression to that of lineage-associated transcription factors (TFs) and identify GFRA2 and BST1 as markers of early B cells. Functional analyses in vitro and in vivo as well as single-cell gene expression analyses supported that surface expression of these proteins defined distinct subpopulations that include cells from both the classical common LPs (CLPs) and Fraction A compartments. The formation of the GFRA2-expressing stages of development depended on the TF EBF1, critical both for the activation of stage-specific target genes and modulation of the epigenetic landscape. Our data show that consecutive expression of Ly6D, GFRA2, and BST1 defines a developmental trajectory linking the CLP to the CD19 progenitor compartment.
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http://dx.doi.org/10.1084/jem.20171384DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028518PMC
July 2018

Transcription factor ID2 prevents E proteins from enforcing a naïve T lymphocyte gene program during NK cell development.

Sci Immunol 2018 04;3(22)

Department of Pathology and Committee on Immunology, University of Chicago, Chicago, IL 60657, USA.

All innate lymphoid cells (ILCs) require the small helix-loop-helix transcription factor ID2, but the functions of ID2 are not well understood in these cells. We show that mature natural killer (NK) cells, the prototypic ILCs, developed in mice lacking ID2 but remained as precursor CD27CD11b cells that failed to differentiate into CD27CD11b cytotoxic effectors. We show that ID2 limited chromatin accessibility at E protein binding sites near naïve T lymphocyte-associated genes including multiple chemokine receptors, cytokine receptors, and signaling molecules and altered the NK cell response to inflammatory cytokines. In the absence of ID2, CD27CD11b NK cells expressed ID3, a helix-loop-helix protein associated with naïve T cells, and they transitioned from a CD8 memory precursor-like to a naïve-like chromatin accessibility state. We demonstrate that ID3 was required for the development of ID2-deficient NK cells, indicating that completely unfettered E protein function is incompatible with NK cell development. These data solidify the roles of ID2 and ID3 as mediators of effector and naïve gene programs, respectively, and revealed a critical role for ID2 in promoting a chromatin state and transcriptional program in CD27CD11b NK cells that supports cytotoxic effector differentiation and cytokine responses.
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http://dx.doi.org/10.1126/sciimmunol.aao2139DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750718PMC
April 2018

Pseudouridylation of tRNA-Derived Fragments Steers Translational Control in Stem Cells.

Cell 2018 05 5;173(5):1204-1216.e26. Epub 2018 Apr 5.

Division of Molecular Hematology, Department of Laboratory Medicine, Lund Stem Cell Center, Faculty of Medicine, Lund University, Lund, Sweden. Electronic address:

Pseudouridylation (Ψ) is the most abundant and widespread type of RNA epigenetic modification in living organisms; however, the biological role of Ψ remains poorly understood. Here, we show that a Ψ-driven posttranscriptional program steers translation control to impact stem cell commitment during early embryogenesis. Mechanistically, the Ψ "writer" PUS7 modifies and activates a novel network of tRNA-derived small fragments (tRFs) targeting the translation initiation complex. PUS7 inactivation in embryonic stem cells impairs tRF-mediated translation regulation, leading to increased protein biosynthesis and defective germ layer specification. Remarkably, dysregulation of this posttranscriptional regulatory circuitry impairs hematopoietic stem cell commitment and is common to aggressive subtypes of human myelodysplastic syndromes. Our findings unveil a critical function of Ψ in directing translation control in stem cells with important implications for development and disease.
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http://dx.doi.org/10.1016/j.cell.2018.03.008DOI Listing
May 2018

deficiency-induced bone marrow niche alterations lead to the initiation of myeloproliferative neoplasm.

Blood Adv 2018 03;2(5):534-548

Center for Hematology and Regenerative Medicine, Department of Medicine, Karolinska University Hospital, and.

Mutations of signal-induced proliferation-associated gene 1 (), a RAP1 GTPase-activating protein, were reported in patients with juvenile myelomonocytic leukemia, a childhood myelodysplastic/myeloproliferative neoplasm (MDS/MPN). deficiency in mice leads to the development of age-dependent MPN. However, expression in bone marrow (BM) microenvironment and its effect on the pathogenesis of MPN remain unclear. We here report that is expressed in human and mouse BM stromal cells and downregulated in these cells from patients with MPN or MDS/MPN at diagnosis. By using the MPN mouse model, we find that deletion causes phenotypic and functional alterations of BM mesenchymal stem and progenitor cells prior to the initiation of the MPN. Importantly, the altered BM niche is required for the development of MDS/MPN following transplantation of normal hematopoietic cells. RNA sequencing reveals an enhanced inflammatory cytokine signaling and dysregulated , , , , and in the BM cellular niches. Our data suggest that expression in the BM niche is critical for maintaining BM niche homeostasis. Moreover, loss-induced BM niche alterations likely enable evolution of clonal hematopoiesis to the hematological malignancies. Therefore, restoring expression or modulating the altered signaling pathways involved might offer therapeutic potential for MPN.
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http://dx.doi.org/10.1182/bloodadvances.2017013599DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5851419PMC
March 2018

Regulatory T cells characterized by low Id3 expression are highly suppressive and accumulate during chronic infection.

Oncotarget 2017 Nov 27;8(61):102835-102851. Epub 2017 Oct 27.

Center for Chronic Immunodeficiency (CCI), Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany.

Foxp3 regulatory T (Treg) cells are broadly divided into naive-like and activated Treg cells, however recent studies suggest further Treg cell heterogeneity. Treg cells contribute to impaired T cell responses in chronic infections, but the role of specific Treg cell subpopulations in viral infections is not well defined. Here, we report that activated Treg cells are separated into two transcriptionally distinct subpopulations characterized by low or high expression of the transcriptional regulator . Treg cells are a highly suppressive Treg cell subpopulation, expressing elevated levels of immunomodulatory molecules and are capable of broadly targeting T cell responses. Viral infection and interleukin-2 promote the differentiation of into Treg cells and during chronic infection Treg cells are the predominant Treg cell population. Thus, our report provides a framework, in which different activated Treg cell subpopulations specifically affect immune responses, possibly contributing to T cell dysfunction in chronic infections.
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http://dx.doi.org/10.18632/oncotarget.22159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732693PMC
November 2017

Don't judge a cell by its cover: heterogeneity within early lymphoid progenitors.

EMBO J 2017 12 30;36(24):3552-3554. Epub 2017 Nov 30.

Lund Stem Cell Center, Lund University, Lund, Sweden.

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http://dx.doi.org/10.15252/embj.201798443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5730884PMC
December 2017

EZH2 Regulates the Developmental Timing of Effectors of the Pre-Antigen Receptor Checkpoints.

J Immunol 2017 06 10;198(12):4682-4691. Epub 2017 May 10.

Committee on Immunology, The University of Chicago, Chicago, IL 60637;

The histone methyltransferase EZH2 is required for B and T cell development; however, the molecular mechanisms underlying this requirement remain elusive. In a murine model of lymphoid-specific EZH2 deficiency we found that EZH2 was required for proper development of adaptive, but not innate, lymphoid cells. In adaptive lymphoid cells EZH2 prevented the premature expression of and the consequent stabilization of p53, an effector of the pre-Ag receptor checkpoints. Deletion of in EZH2-deficient lymphocytes prevented p53 stabilization, extended lymphocyte survival, and restored differentiation resulting in the generation of mature B and T lymphocytes. Our results uncover a crucial role for EZH2 in adaptive lymphocytes to control the developmental timing of effectors of the pre-Ag receptor checkpoints.
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http://dx.doi.org/10.4049/jimmunol.1700319DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5527689PMC
June 2017

Cellular plasticity in B-cell leukemia.

Cell Cycle 2017 03 24;16(6):495-496. Epub 2017 Jan 24.

a Department of Clinical and Experimental Medicine , Experimental Hematopoiesis Unit, Faculty of Health Sciences, Linköping University , Linköping , Sweden.

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http://dx.doi.org/10.1080/15384101.2017.1285635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5384590PMC
March 2017

Id3 Maintains Foxp3 Expression in Regulatory T Cells by Controlling a Transcriptional Network of E47, Spi-B, and SOCS3.

Cell Rep 2016 12;17(11):2827-2836

Center for Chronic Immunodeficiency (CCI), Faculty of Medicine, University Medical Center Freiburg, 79106 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany. Electronic address:

The transcription factor Foxp3 dominantly controls regulatory T (Treg) cell function, and only its continuous expression guarantees the maintenance of full Treg cell-suppressive capacity. However, transcriptional regulators maintaining Foxp3 transcription are incompletely described. Here, we report that high E47 transcription factor activity in Treg cells resulted in unstable Foxp3 expression. Under homeostatic conditions, Treg cells expressed high levels of the E47 antagonist Id3, thus restricting E47 activity and maintaining Foxp3 expression. In contrast, stimulation of Id3-deficient or E47-overexpressing Treg cells resulted in the loss of Foxp3 expression in a subset of Treg cells in vivo and in vitro. Mechanistic analysis indicated that E47 activated expression of the transcription factor Spi-B and the suppressor of cytokine signaling 3 (SOCS3), which both downregulated Foxp3 expression. These findings demonstrate that the balance of Id3 and E47 controls the maintenance of Foxp3 expression in Treg cells and, thus, contributes to Treg cell plasticity.
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http://dx.doi.org/10.1016/j.celrep.2016.11.045DOI Listing
December 2016

Clonal conversion of B lymphoid leukemia reveals cross-lineage transfer of malignant states.

Genes Dev 2016 11 2;30(22):2486-2499. Epub 2016 Dec 2.

Department of Clinical and Experimental Medicine, Experimental Hematopoiesis Unit, Faculty of Health Sciences, Linköping University, 58183 Linkoping, Sweden.

Even though leukemia is considered to be confined to one specific hematopoietic cell type, cases of acute leukemia of ambiguous lineage and patients relapsing in phenotypically altered disease suggest that a malignant state may be transferred between lineages. Because B-cell leukemia is associated with mutations in transcription factors of importance for stable preservation of lineage identity, we here investigated the potential lineage plasticity of leukemic cells. We report that primary pro-B leukemia cells from mice carrying heterozygous mutations in either or both the Pax5 and Ebf1 genes, commonly mutated in human leukemia, can be converted into T lineage leukemia cells. Even though the conversion process involved global changes in gene expression and lineage-restricted epigenetic reconfiguration, the malignant phenotype of the cells was preserved, enabling them to expand as T lineage leukemia cells in vivo. Furthermore, while the transformed pro-B cells displayed plasticity toward myeloid lineages, the converted cells failed to cause myeloid leukemia after transplantation. These data provide evidence that a malignant phenotype can be transferred between hematopoietic lineages. This has important implications for modern cancer medicine because lineage targeted treatment of leukemia patients can be predicted to provoke the emergence of phenotypically altered subclones, causing clinical relapse.
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http://dx.doi.org/10.1101/gad.285536.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5159664PMC
November 2016

Superenhancer reprogramming drives a B-cell-epithelial transition and high-risk leukemia.

Genes Dev 2016 09;30(17):1971-90

Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA;

IKAROS is required for the differentiation of highly proliferative pre-B-cell precursors, and loss of IKAROS function indicates poor prognosis in precursor B-cell acute lymphoblastic leukemia (B-ALL). Here we show that IKAROS regulates this developmental stage by positive and negative regulation of superenhancers with distinct lineage affiliations. IKAROS defines superenhancers at pre-B-cell differentiation genes together with B-cell master regulators such as PAX5, EBF1, and IRF4 but is required for a highly permissive chromatin environment, a function that cannot be compensated for by the other transcription factors. IKAROS is also highly enriched at inactive enhancers of genes normally expressed in stem-epithelial cells. Upon IKAROS loss, expression of pre-B-cell differentiation genes is attenuated, while a group of extralineage transcription factors that are directly repressed by IKAROS and depend on EBF1 relocalization at their enhancers for expression is induced. LHX2, LMO2, and TEAD-YAP1, normally kept separate from native B-cell transcription regulators by IKAROS, now cooperate directly with them in a de novo superenhancer network with its own feed-forward transcriptional reinforcement. Induction of de novo superenhancers antagonizes Polycomb repression and superimposes aberrant stem-epithelial cell properties in a B-cell precursor. This dual mechanism of IKAROS regulation promotes differentiation while safeguarding against a hybrid stem-epithelial-B-cell phenotype that underlies high-risk B-ALL.
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http://dx.doi.org/10.1101/gad.283762.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5066240PMC
September 2016

Identification of Stage-Specific Surface Markers in Early B Cell Development Provides Novel Tools for Identification of Progenitor Populations.

J Immunol 2016 09 25;197(5):1937-44. Epub 2016 Jul 25.

Department of Molecular Hematology, Lund University, 22184 Lund, Sweden; and Department of Clinical and Experimental Medicine, Linköping University, 58185 Linköping, Sweden

Whereas the characterization of B lymphoid progenitors has been facilitated by the identification of lineage- and stage-specific surface markers, the continued identification of differentially expressed proteins increases our capacity to explore normal and malignant B cell development. To identify novel surface markers with stage-specific expression patterns, we explored the reactivity of CD19(+) B cell progenitor cells to Abs targeted to 176 surface proteins. Markers with stage-specific expression were identified using a transgenic reporter gene system subdividing the B cell progenitors into four surface IgM(-) stages. This approach affirmed the utility of known stage-specific markers, as well as identifying additional proteins that selectively marked defined stages of B cell development. Among the stage-specific markers were the cell adhesion proteins CD49E, CD11A, and CD54 that are highly expressed selectively on the most immature progenitors. This work identifies a set of novel stage-specific surface markers that can be used as a complement to the classical staining protocols to explore B lymphocyte development.
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http://dx.doi.org/10.4049/jimmunol.1600297DOI Listing
September 2016

Type 1 Diabetes Mellitus Donor Mesenchymal Stromal Cells Exhibit Comparable Potency to Healthy Controls In Vitro.

Stem Cells Transl Med 2016 Nov 13;5(11):1485-1495. Epub 2016 Jul 13.

Center for Hematology and Regenerative Medicine, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden

: Bone marrow mesenchymal stromal cells (BM-MSCs) have been characterized and used in many clinical studies based on their immunomodulatory and regenerative properties. We have recently reported the benefit of autologous MSC systemic therapy in the treatment of type 1 diabetes mellitus (T1D). Compared with allogeneic cells, use of autologous products reduces the risk of eliciting undesired complications in the recipient, including rejection, immunization, and transmission of viruses and prions; however, comparable potency of autologous cells is required for this treatment approach to remain feasible. To date, no analysis has been reported that phenotypically and functionally characterizes MSCs derived from newly diagnosed and late-stage T1D donors in vitro with respect to their suitability for systemic immunotherapy. In this study, we used gene array in combination with functional in vitro assays to address these questions. MSCs from T1D donors and healthy controls were expanded from BM aspirates. BM mononuclear cell counts and growth kinetics were comparable between the groups, with equivalent colony-forming unit-fibroblast capacity. Gene microarrays demonstrated differential gene expression between healthy and late-stage T1D donors in relation to cytokine secretion, immunomodulatory activity, and wound healing potential. Despite transcriptional differences, T1D MSCs did not demonstrate a significant difference from healthy controls in immunosuppressive activity, migratory capacity, or hemocompatibility. We conclude that despite differential gene expression, expanded MSCs from T1D donors are phenotypically and functionally similar to healthy control MSCs with regard to their immunomodulatory and migratory potential, indicating their suitability for use in autologous systemic therapy.

Significance: The potential for mesenchymal stromal cells (MSCs) as a cell-based therapy in the treatment of immunologic disorders has been well established. Recent studies reported the clinical potential for autologous MSCs as a systemic therapy in the treatment of type I diabetes mellitus (T1D). The current study compared the genotypic and phenotypic profiles of bone marrow-derived MSCs from T1D and healthy donors as autologous (compared with allogeneic) therapy provides distinct advantages, such as reduced risk of immune reaction and transmission of infectious agents. The findings of the current study demonstrate that despite moderate differences in T1D MSCs at the gene level, these cells can be expanded in culture to an extent corresponding to that of MSCs derived from healthy donors. No functional difference in terms of immunosuppressive activity, blood compatibility, or migratory capacity was evident between the groups. The study findings also show that autologous MSC therapy holds promise as a T1D treatment and should be evaluated further in clinical trials.
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http://dx.doi.org/10.5966/sctm.2015-0272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5070499PMC
November 2016

Early onset combined immunodeficiency and autoimmunity in patients with loss-of-function mutation in LAT.

J Exp Med 2016 06 30;213(7):1185-99. Epub 2016 May 30.

Monique and Jacques Roboh Department of Genetic Research, Hadassah Medical Center, Hebrew University, Jerusalem 91120, Israel Department of Pediatric Hematology-Oncology and Bone Marrow Transplantation, Hadassah Medical Center, Hebrew University, Jerusalem 91120, Israel

The adapter protein linker for activation of T cells (LAT) is a critical signaling hub connecting T cell antigen receptor triggering to downstream T cell responses. In this study, we describe the first kindred with defective LAT signaling caused by a homozygous mutation in exon 5, leading to a premature stop codon deleting most of the cytoplasmic tail of LAT, including the critical tyrosine residues for signal propagation. The three patients presented from early childhood with combined immunodeficiency and severe autoimmune disease. Unlike in the mouse counterpart, reduced numbers of T cells were present in the patients. Despite the reported nonredundant role of LAT in Ca(2+) mobilization, residual T cells were able to induce Ca(2+) influx and nuclear factor (NF) κB signaling, whereas extracellular signal-regulated kinase (ERK) signaling was completely abolished. This is the first report of a LAT-related disease in humans, manifesting by a progressive combined immune deficiency with severe autoimmune disease.
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http://dx.doi.org/10.1084/jem.20151110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4925012PMC
June 2016