Cell identity is orchestrated through an interplay between transcription factor (TF) action and genome architecture. The mechanisms used by TFs to shape three-dimensional (3D) genome organization remain incompletely understood. Here we present evidence that the lineage-instructive TF CEBPA drives extensive chromatin compartment switching and promotes the formation of long-range chromatin hubs during induced B cell-to-macrophage transdifferentiation. Mechanistically, we find that the intrinsically disordered region (IDR) of CEBPA undergoes in vitro phase separation (PS) dependent on aromatic residues. Both overexpressing B cells and native CEBPA-expressing cell types such as primary granulocyte-macrophage progenitors, liver cells, and trophectoderm cells reveal nuclear CEBPA foci and long-range 3D chromatin hubs at CEBPA-bound regions. In short, we show that CEBPA can undergo PS through its IDR, which may underlie in vivo foci formation and suggest a potential role of PS in regulating CEBPA function., We thank the Graf lab members for helpful discussions, and the CRG Genomics, Flow Cytometry and Advanced Light Microscopy core facilities; M.C.-K. was supported by an EMBO postdoctoral fellowship (ALTF 1057-2019) and PCIN-MSCA-fellowship (Ministerio de Ciencia e Innovación PCI2021-122032-2B). S.C. is supported by a “La Caixa” Junior Leader fellowship, by the Jérôme Lejeune Foundation (JLF#1902) and the Spanish Ministry of Science and Innovation (PID2020-117950RA-I00). G.S. was supported by the “Fundación Científica de la Asociación Española Contra el Cáncer.” M.V.N. was supported by People Program (Marie Curie Actions) FP7/2007–2013 under REA grant 6089 and Juan de la Cierva-Incorporación 2017. C.G.-C. acknowledges a graduate fellowship from MINECO (PRE2018-084684). X.S. acknowledges funding from AGAUR (2017 SGR 324), MINECO (BIO2015-70092-R and PID2019-110198RB-I00), and the European Research Council (CONCERT, contract number 648201). This work was funded by the Max Planck Society and partially supported by grants from the Deutsche Forschungsgemeinschaft (DFG) SPP2202 Priority Program Grant HN 4/1-1 (to D.H.) and by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) Plan Estatal 2015, SAF.2015-68740-P (to T.G.). We acknowledge support by the Spanish Ministry of Science and Innovation, to the EMBL partnership, the Centro de Excelencia Severo Ochoa, the Josep Carreras Foundation, and the CERCA Programme / Generalitat de Catalunya.

Cell identity is orchestrated through an interplay between transcription factor (TF) action and genome architecture. The mechanisms used by TFs to shape three-dimensional (3D) genome organization remain incompletely understood. Here we present evidence that the lineage-instructive TF CEBPA drives extensive chromatin compartment switching and promotes the formation of long-range chromatin hubs during induced B cell-to-macrophage transdifferentiation. Mechanistically, we find that the intrinsically disordered region (IDR) of CEBPA undergoes in vitro phase separation (PS) dependent on aromatic residues. Both overexpressing B cells and native CEBPA-expressing cell types such as primary granulocyte-macrophage progenitors, liver cells, and trophectoderm cells reveal nuclear CEBPA foci and long-range 3D chromatin hubs at CEBPA-bound regions. In short, we show that CEBPA can undergo PS through its IDR, which may underlie in vivo foci formation and suggest a potential role of PS in regulating CEBPA function.

Children with Down syndrome (DS, trisomy 21) are at a significantly higher risk of developing acute leukemia compared to the overall population. Many studies investigating the link between trisomy 21 and leukemia initiation and progression have been conducted over the last two decades. Despite improved treatment regimens and significant progress in iden - tifying genes on chromosome 21 and the mechanisms by which they drive leukemogenesis, there is still much that is unknown. A focused group of scientists and clinicians with expertise in leukemia and DS met in October 2022 at the Jérôme Lejeune Foundation in Paris, France for the 1st International Symposium on Down Syndrome and Leukemia. This meeting was held to discuss the most recent advances in treatment regimens and the biology underlying the initiation, progression, and relapse of acute lymphoblastic leukemia and acute myeloid leukemia in children with DS. This review provides a summary of what is known in the field, challenges in the management of DS patients with leukemia, and key questions in the field.

Short-chain fatty acids (SCFAs) are immunomodulatory compounds produced by the microbiome through dietary fiber fermentation. Although generally considered beneficial for gut health, patients suffering from inflammatory bowel disease (IBD) display poor tolerance to fiber-rich diets, suggesting that SCFAs may have contrary effects under inflammatory conditions. To investigate this, we examined the effect of SCFAs on human macrophages in the presence of Toll-like receptor (TLR) agonists. In contrast to anti-inflammatory effects under steady-state conditions, we found that butyrate and propionate activated the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in the presence of TLR agonists. Mechanistically, these SCFAs prevented transcription of FLICE-like inhibitory protein (cFLIP) and interleukin-10 (IL-10) through histone deacetylase (HDAC) inhibition, triggering caspase-8-dependent NLRP3 inflammasome activation. SCFA-driven NLRP3 activation was potassium efflux independent and did not result in cell death but rather triggered hyperactivation and IL-1β release. Our findings demonstrate that butyrate and propionate are bacterially derived danger signals that regulate NLRP3 inflammasome activation through epigenetic modulation of the inflammatory response.

Cell identity is orchestrated through an interplay between transcription factor (TF) action and genome architecture. The mechanisms used by TFs to shape three-dimensional (3D) genome organization remain incompletely understood. Here we present evidence that the lineage-instructive TF CEBPA drives extensive chromatin compartment switching and promotes the formation of long-range chromatin hubs during induced B cell-to-macrophage transdifferentiation. Mechanistically, we find that the intrinsically disordered region (IDR) of CEBPA undergoes in vitro phase separation (PS) dependent on aromatic residues. Both overexpressing B cells and native CEBPA-expressing cell types such as primary granulocyte-macrophage progenitors, liver cells, and trophectoderm cells reveal nuclear CEBPA foci and long-range 3D chromatin hubs at CEBPA-bound regions. In short, we show that CEBPA can undergo PS through its IDR, which may underlie in vivo foci formation and suggest a potential role of PS in regulating CEBPA function., We thank the Graf lab members for helpful discussions, and the CRG Genomics, Flow Cytometry and Advanced Light Microscopy core facilities; M.C.-K. was supported by an EMBO postdoctoral fellowship (ALTF 1057-2019) and PCIN-MSCA-fellowship (Ministerio de Ciencia e Innovación PCI2021-122032-2B). S.C. is supported by a “La Caixa” Junior Leader fellowship, by the Jérôme Lejeune Foundation (JLF#1902) and the Spanish Ministry of Science and Innovation (PID2020-117950RA-I00). G.S. was supported by the “Fundación Científica de la Asociación Española Contra el Cáncer.” M.V.N. was supported by People Program (Marie Curie Actions) FP7/2007–2013 under REA grant 6089 and Juan de la Cierva-Incorporación 2017. C.G.-C. acknowledges a graduate fellowship from MINECO (PRE2018-084684). X.S. acknowledges funding from AGAUR (2017 SGR 324), MINECO (BIO2015-70092-R and PID2019-110198RB-I00), and the European Research Council (CONCERT, contract number 648201). This work was funded by the Max Planck Society and partially supported by grants from the Deutsche Forschungsgemeinschaft (DFG) SPP2202 Priority Program Grant HN 4/1-1 (to D.H.) and by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) Plan Estatal 2015, SAF.2015-68740-P (to T.G.). We acknowledge support by the Spanish Ministry of Science and Innovation, to the EMBL partnership, the Centro de Excelencia Severo Ochoa, the Josep Carreras Foundation, and the CERCA Programme / Generalitat de Catalunya.