Epigenetic control of haematopoiesis

  • GroupJLSardina
+34 935 572 800
Campus ICO-Germans Trias i Pujol

Josep Carreras Leukaemia Research Institute
Can Ruti Campus
Ctra de Can Ruti, Camí de les Escoles s/n
08916 Badalona, Barcelona
Spain

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Summary

Cell fate decisions, such as haematopoietic differentiation, are typically initiated by transcription factors that regulate gene expression in concert with epigenetic modifications, which include histone and DNA modifications. DNA methylation related genes including DNMT3A or TET2 are among the most frequently mutated genes in blood malignancies. Traditionally, studies aimed at understanding the effect of aberrant DNA methylation in cancer patients have focused on gene promoters and gene bodies. However, we and others have recently described that the most DNA methylation-dynamic regions are located distally from the genes (at enhancer elements), coinciding with their preferential binding by DNMT3A and TET2. Therefore, how aberrant DNA methylation dynamics impact on the chromatin structure at distal regulatory regions during blood cancer onset and progression remains to be fully elucidated. 

Research

Research in our group is aimed to uncover the epigenetic mechanisms governing haematopoietic cell fate decisions, with a special interest in those leading to the onset and development of blood malignancies (including leukaemia and myelodysplastic syndromes among others)

Lines of research:

1. Study of the interplay between DNA (hydroxy)methylation and chromatin dynamics at distal gene regulatory regions during hematopoietic cell fate decisions.

2. Uncovering the role of TET2 in the epigenetic control of the chromatin at distal gene regulatory regions during leukemic onset and progression.

3. Deciphering the molecular mechanisms underlying 5hmC-mediated chromatin compaction during cell fate decisions.

4. Study of the role of mRNA methylation-mediated post-transcriptional control during myeloid cell differentiation.

We are currently looking for highly motivated PhD students to join our group. Please contact José Luis Sardina (jsardina@carrerasresearch.orgfor further information

People

Selected publications

Xiu Y, Dong Q, Fu L, Bossler A, Tang X, Boyce B, Borcherding N, Leidinger M, Sardina JL, Xue HH, Li Q, Feldman A, Aifantis I, Boccalatte F, Wang L, Jin M, Khoury J, Wang W, Hu S, Yuan Y, Wang E, Yuan J, Janz S, Colgan J, Habelhah H, Waldschmidt T, Müschen M, Bagg A, Darbro B, Zhao C.

Coactivation of NF-κB and Notch signaling is sufficient to induce B-cell transformation and enables B-myeloid conversion.

Blood. 2020 Jan 9;135(2):108-120 , .
NF-κB and Notch signaling can be simultaneously activated in a variety of B-cell lymphomas. Patients with B-cell lymphoma occasionally develop clonally related myeloid tumors with poor prognosis. Whether concurrent activation of both pathways is sufficient to induce B-cell transformation and whether the signaling initiates B-myeloid conversion in a pathological context are largely unknown. Here, we provide genetic evidence that concurrent activation of NF-κB and Notch signaling in committed B cells is sufficient to induce B-cell lymphomatous transformation and primes common progenitor cells to convert to myeloid lineage through dedifferentiation, not transdifferentiation. Intriguingly, the converted myeloid cells can further transform, albeit at low frequency, into myeloid leukemia. Mechanistically, coactivation of NF-κB and Notch signaling endows committed B cells with the ability to self renew. Downregulation of BACH2, a lymphoma and myeloid gene suppressor, but not upregulation of CEBPα and/or downregulation of B-cell transcription factors, is an early event in both B-cell transformation and myeloid conversion. Interestingly, a DNA hypomethylating drug not only effectively eliminated the converted myeloid leukemia cells, but also restored the expression of green fluorescent protein, which had been lost in converted myeloid leukemia cells. Collectively, our results suggest that targeting NF-κB and Notch signaling will not only improve lymphoma treatment, but also prevent the lymphoma-to-myeloid tumor conversion. Importantly, DNA hypomethylating drugs might efficiently treat these converted myeloid neoplasms.
Tian TV, Di Stefano B, Stik G, Vila-Casadesús M, Sardina JL, Vidal E, Dasti A, Segura-Morales C, De Andrés-Aguayo L, Gómez A, Goldmann J, Jaenisch R, Graf T.

Whsc1 links pluripotency exit with mesendoderm specification.

Nat Cell Biol. 2019 Jul;21(7):824-834 , .
How pluripotent stem cells differentiate into the main germ layers is a key question of developmental biology. Here, we show that the chromatin-related factor Whsc1 (also known as Nsd2 and MMSET) has a dual role in pluripotency exit and germ layer specification of embryonic stem cells. On induction of differentiation, a proportion of Whsc1-depleted embryonic stem cells remain entrapped in a pluripotent state and fail to form mesendoderm, although they are still capable of generating neuroectoderm. These functions of Whsc1 are independent of its methyltransferase activity. Whsc1 binds to enhancers of the mesendodermal regulators Gata4, T (Brachyury), Gata6 and Foxa2, together with Brd4, and activates the expression of these genes. Depleting each of these regulators also delays pluripotency exit, suggesting that they mediate the effects observed with Whsc1. Our data indicate that Whsc1 links silencing of the pluripotency regulatory network with activation of mesendoderm lineages.
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Sardina JL, Collombet S, Tian TV, Gómez A, Di Stefano B, Berenguer C, Brumbaugh J, Stadhouders R, Segura-Morales C, Gut M, Gut IG, Heath S, Aranda S, Di Croce L, Hochedlinger K, Thieffry D, Graf T.

Transcription Factors Drive Tet2-Mediated Enhancer Demethylation to Reprogram Cell Fate.

Cell Stem Cell. 2018 Nov 1;23(5):727-741.e9 , .
Here, we report DNA methylation and hydroxymethylation dynamics at nucleotide resolution using C/EBPα-enhanced reprogramming of B cells into induced pluripotent cells (iPSCs). We observed successive waves of hydroxymethylation at enhancers, concomitant with a decrease in DNA methylation, suggesting active demethylation. Consistent with this finding, ablation of the DNA demethylase Tet2 almost completely abolishes reprogramming. C/EBPα, Klf4, and Tfcp2l1 each interact with Tet2 and recruit the enzyme to specific DNA sites. During reprogramming, some of these sites maintain high levels of 5hmC, and enhancers and promoters of key pluripotency factors become demethylated as early as 1 day after Yamanaka factor induction. Surprisingly, methylation changes precede chromatin opening in distinct chromatin regions, including Klf4 bound sites, revealing a pioneer factor activity associated with alternation in DNA methylation. Rapid changes in hydroxymethylation similar to those in B cells were also observed during compound-accelerated reprogramming of fibroblasts into iPSCs, highlighting the generality of our observations.
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Collombet S, van Oevelen C, Sardina Ortega JL, Abou-Jaoudé W, Di Stefano B, Thomas-Chollier M, Graf T, Thieffry D.

Logical modeling of lymphoid and myeloid cell specification and transdifferentiation.

Proc Natl Acad Sci U S A. 2017 Jun 6;114(23):5792-5799 , .
Blood cells are derived from a common set of hematopoietic stem cells, which differentiate into more specific progenitors of the myeloid and lymphoid lineages, ultimately leading to differentiated cells. This developmental process is controlled by a complex regulatory network involving cytokines and their receptors, transcription factors, and chromatin remodelers. Using public data and data from our own molecular genetic experiments (quantitative PCR, Western blot, EMSA) or genome-wide assays (RNA-sequencing, ChIP-sequencing), we have assembled a comprehensive regulatory network encompassing the main transcription factors and signaling components involved in myeloid and lymphoid development. Focusing on B-cell and macrophage development, we defined a qualitative dynamical model recapitulating cytokine-induced differentiation of common progenitors, the effect of various reported gene knockdowns, and the reprogramming of pre-B cells into macrophages induced by the ectopic expression of specific transcription factors. The resulting network model can be used as a template for the integration of new hematopoietic differentiation and transdifferentiation data to foster our understanding of lymphoid/myeloid cell-fate decisions.
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Sardina JL, Di Stefano B, Graf T.

How does C/EBPα speed up cell reprogramming?

Cell Cycle. 2016 Sep 16;15(18):2381-2 , .
No abstract available
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Di Stefano B, Collombet S, Jakobsen JS, Wierer M, Sardina JL, Lackner A, Stadhouders R, Segura-Morales C, Francesconi M, Limone F, Mann M, Porse B, Thieffry D, Graf T.

C/EBPα creates elite cells for iPSC reprogramming by upregulating Klf4 and increasing the levels of Lsd1 and Brd4.

Nat Cell Biol. 2016 Apr;18(4):371-81 , .
Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) is typically inefficient and has been explained by elite-cell and stochastic models. We recently reported that B cells exposed to a pulse of C/EBPα (Bα' cells) behave as elite cells, in that they can be rapidly and efficiently reprogrammed into iPSCs by the Yamanaka factors OSKM. Here we show that C/EBPα post-transcriptionally increases the abundance of several hundred proteins, including Lsd1, Hdac1, Brd4, Med1 and Cdk9, components of chromatin-modifying complexes present at super-enhancers. Lsd1 was found to be required for B cell gene silencing and Brd4 for the activation of the pluripotency program. C/EBPα also promotes chromatin accessibility in pluripotent cells and upregulates Klf4 by binding to two haematopoietic enhancers. Bα' cells share many properties with granulocyte/macrophage progenitors, naturally occurring elite cells that are obligate targets for leukaemic transformation, whose formation strictly requires C/EBPα.
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Bueno C, Sardina JL, Di Stefano B, Romero-Moya D, Muñoz-López A, Ariza L, Chillón MC, Balanzategui A, Castaño J, Herreros A, Fraga MF, Fernández A, Granada I, Quintana-Bustamante O, Segovia JC, Nishimura K, Ohtaka M, Nakanishi M, Graf T, Menendez P.

Reprogramming human B cells into induced pluripotent stem cells and its enhancement by C/EBPα.

Leukemia. 2016 Mar;30(3):674-82 , .
B cells have been shown to be refractory to reprogramming and B-cell-derived induced pluripotent stem cells (iPSC) have only been generated from murine B cells engineered to carry doxycycline-inducible Oct4, Sox2, Klf4 and Myc (OSKM) cassette in every tissue and from EBV/SV40LT-immortalized lymphoblastoid cell lines. Here, we show for the first time that freshly isolated non-cultured human cord blood (CB)- and peripheral blood (PB)-derived CD19+CD20+ B cells can be reprogrammed to iPSCs carrying complete VDJH immunoglobulin (Ig) gene monoclonal rearrangements using non-integrative tetracistronic, but not monocistronic, OSKM-expressing Sendai Virus. Co-expression of C/EBPα with OSKM facilitates iPSC generation from both CB- and PB-derived B cells. We also demonstrate that myeloid cells are much easier to reprogram than B and T lymphocytes. Differentiation potential back into the cell type of their origin of B-cell-, T-cell-, myeloid- and fibroblast-iPSCs is not skewed, suggesting that their differentiation does not seem influenced by 'epigenetic memory'. Our data reflect the actual cell-autonomous reprogramming capacity of human primary B cells because biased reprogramming was avoided by using freshly isolated primary cells, not exposed to cytokine cocktails favoring proliferation, differentiation or survival. The ability to reprogram CB/PB-derived primary human B cells offers an unprecedented opportunity for studying developmental B lymphopoiesis and modeling B-cell malignancies.
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