Project description:Fibrosis in the lung is thought to be driven by epithelial cell dysfunction and aberrant cell-cell interactions. Unveiling the molecular mechanisms of cellular plasticity and cell-cell interactions is imperative to elucidating lung regenerative capacity and aberrant repair in pulmonary fibrosis. By mining publicly available RNA-Seq data sets, we identified loss of CCAAT enhancer-binding protein alpha (CEBPA) as a candidate contributor to idiopathic pulmonary fibrosis (IPF). We used conditional KO mice, scRNA-Seq, lung organoids, small-molecule inhibition, and potentially novel gene manipulation methods to investigate the role of CEBPA in lung fibrosis and repair. Long-term (6 months or more) of Cebpa loss in AT2 cells caused spontaneous fibrosis and increased susceptibility to bleomycin-induced fibrosis. Cebpa knockout (KO) in these mice significantly decreased AT2 cell numbers in the lung and reduced expression of surfactant homeostasis genes, while increasing inflammatory cell recruitment as well as upregulating S100a8/a9 in AT2 cells. In vivo treatment with an S100A8/A9 inhibitor alleviated experimental lung fibrosis. Restoring CEBPA expression in lung organoids ex vivo and during experimental lung fibrosis in vivo rescued CEBPA deficiency-mediated phenotypes. Our study establishes a direct mechanistic link between CEBPA repression, impaired AT2 cell identity, disrupted tissue homeostasis, and lung fibrosis.
Project description:C/EBPalpha is a transcription factor critically involved in myeloid development and indispensable for formation of granulocytes. To track the cellular fate of stem and progenitor (LSK) cells, which express C/EBPalpha, we developed a mouse model expressing Cre recombinase from the Cebpa promoter and an inducible EYFP allele. We show that Cebpa/EYFP+ cells represent a significant subset of LSK cells, which predominantly give rise to myeloid cells in steady state hematopoiesis. C/EBPalpha induced a robust myeloid gene expression signature and downregulated E2A-induced regulators of early lymphoid development. In addition, Cebpa/EYFP+ cells comprise a fraction of early thymic progenitors (ETP) with robust myeloid potential. However, Cebpa/EYFP+ LSK and ETP cells retained the ability to develop into erythroid and T-lymphoid lineages, respectively. These findings support an instructive, but argue against a lineage restrictive role of C/EBPalpha in multipotent hematopoietic and thymic progenitors. We performed global gene expression profiling of double-sorted Cebpa/EYFP+ and Cebpa/EYFP- LSK cells of pooled Cebpa Cre/wt R26 EYFP reporter mice to identify differentially regulated genes in Cebpa+ versus Cebpa- LSK cells. RNA was isolated from three biological replicates of Cebpa/EYFP+ LSK cells and two biological replicates of Cebpa/EYFP- LSK cells. To determine if the identified genes were truly dependent on Cebpa expression, we also performed global gene expression profilling of Cebpa/EYFP+ and Cebpa/EYFP- fetal liver LSK cells of Cebpa Cre/fl R26 EYFP mice. Induction of Cebpa/Cre expression in these mice leads to Cre-mediated recombination of the floxed wt Cebpa allele resulting in a complete Cebpa knock-out. In this case, RNA was isolated from two biological replicates of either Cebpa/EYFP+ and Cebpa/EYFP- LSK cells. In addition, we included one biological replicate of Cebpa/EYFP+ and Cebpa/EYFP- fetal liver LSK cells of Cebpa Cre/wt R26 EYFP mice to determine the correlation of differentially regulated genes in bone marrow and fetal liver LSK cells.
Project description:The key myeloid transcription factor (TF) CEBPA is frequently mutated in acute myeloid leukemia (AML), but the molecular ramifications of this leukemic driver mutation remain elusive. To investigate CEBPA mutant AML, we compared gene expression changes in human CEBPA mutant AML and in the corresponding CebpaLp30 mouse model, and identified a conserved cross-species transcriptional program. ChIP-seq revealed aberrantly activated enhancers, exclusively occupied by the leukemia-associated CEBPA-p30 isoform. One leukemic-enhancer upstream of Nt5e, encoding CD73, was physically and functionally linked to this conserved AML gene, and could be activated by CEBPA. Targeting of CD73-adenosine signaling increased AML survival in transplanted mice. Our data indicate a first-in-class link between a TF cancer driver mutation and a druggable, direct transcriptional target.
Project description: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. A large intrinsically disordered region (IDR) enables CEBPA to undergo in vitro phase separation and to co-condense with transcriptional partners, which is at least partially mediated by aromatic residues. Furthermore, CEBPA forms visible nuclear condensates in transdifferentiating B cells that co-localize with co-activator condensates and recover rapidly upon photobleaching. Finally, native CEBPA-expressing cell types such as primary granulocyte-macrophage progenitors (GMPs), liver cells and trophectoderm cells also reveal nuclear CEBPA condensates and long-range 3D chromatin hubs at CEBPA-bound regions. These findings support a model in which CEBPA acts as a 3D genome structural organizer and suggest that this effect is mediated at least in part by its phase-separation capacity.
Project description:Many cancer patients don’t benefit from currently-approved immune checkpoint inhibitors (ICI), suggesting that additional immunomodulation of the immunosuppressive tumour microenvironment (TME) is required. MTL-CEBPA specifically upregulates expression of master myeloid transcription factor, CEBPA, relieving myeloid-driven immunosuppression. Here, we report the safety, tolerability, pharmacokinetics, and efficacy of MTL-CEBPA in combination with pembrolizumab in patients with advanced solid tumours that typically show ICI resistance. Multimodal exploratory analyses of paired patient biopsies demonstrate biological changes associated with combination treatment of MTL-CEBPA and pembrolizumab, including increased infiltration of T cell and antigen-presenting cells supporting conversion from an immune desert towards a more immune-inflamed TME. Patients with disease stabilisation demonstrate reductions in immunosuppressive myeloid cells post-treatment. Collectively, these data support a role for MTL-CEBPA in reducing immunosuppression in the TME. This study was registered at ClinicalTrials.gov (NCT04105335). This manuscript also reports proteomic data from patients treated with MTL-CEBPA in combination with sorafenib from clinical trial, OUTREACH, accessible at ClinicalTrials.gov, number NCT02716012 and reported. Stored plasma from patients from this clinical trial were analysed using OLINK as described below.
Project description:Acute Myeloid Leukemia (AML) is a heterogeneous disease from the molecular and biological standpoints, and even patients with a specific gene expression profile may present clinical and molecular heterogeneity. We studied the epigenetic profiles of a cohort of patients that shared a common gene expression profile but differed in that only half of them harbored mutations of the CEBPA locus, while the rest presented with silencing of this gene and co-expression of certain T cell markers. DNA methylation studies revealed that these two groups of patients could be readily segregated in an unsupervised fashion based on their DNA methylation profiles alone. Furthermore, CEBPA silencing was associated with the presence of an aberrant DNA hypermethylation signature, which was not present in the CEBPA mutant group. This aberrant hypermethylation occurred more frequently at sites within CpG islands. CEBPA silenced leukemias also displayed marked hypermethylation when compared with normal CD34+ hematopoietic cells, while CEBPA mutant cases showed only mild changes in DNA methylation when compared to these normal progenitors. Biologically, CEBPA silenced leukemias presented with a decreased response to myeloid growth factors in vitro. Keywords: DNA methylation profiling Direct comparison of DNA methylation in leukemic blasts from 8 patients with Acute Myeloid Leukemia (AML) carrying a CEBPA mutation and 8 patients with AML without CEBPA mutation but with silencing of CEBPA expression. Two control groups are included: 8 CD34+ bone marrow samples from healthy donors and 9 samples of T Acute Lymphoblastic Leukemia (T-ALL) patients.
Project description:Weaker CEBPA binding in the human than in the mouse genome is a general trait of the human genome across multiple biological conditions. Alu repeats carry strong CEBPA binding motifs, which compete with regulatory regions for CEBPA binding. To directly test this hypothesis, we attempted to overcome Alu competition by using, first, a CRISPR-dCas9 system in BLaER1 cells (Rapino et al. 2013). By promoting the recruitment of the inactive Cas9 to Alu regions with specific gRNAs targeting Alu repeats containing strong CEBPA motifs we protected them, hampering CEBPA binding to these regions. We tested the effect of two different paired gRNA constructs in two replicates and one control paired gRNA in two replicates. Second, we also further overexpressed CEBPA in human BLaER1 cells to overcome Alu competition. We tested two doses of CEBPA overexpression in two replicates and one control experiment in two replicates.
Project description:Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal lung disease, characterized by hyperplasia and blocked differentiation of alveolar type-2 cells (AT2s). Here, we found that sobetirome (GC-1), a thyroid hormone receptor β (TRβ) specific agonist, exhibits striking efficiency and safety to treat PF in two mouse models (bleomycin and silica) and one rat model. We proposed that most IPF is a type of non-thyroidal illness syndrome (NTIS) based on hormone level tests. Using lineage tracing mice and co-culture, we confirmed that the anti-fibrosis effect of GC-1 is primarily through modulating the maladaptive activation state AT2s (MAS-AT2s) cell fate, promoting differentiation and inhibiting proliferation. Luciferase and ChiP assays reveal that TRβ with GC-1 directly regulate KLF2 and CEBPA, and further drive the AT1 genes expression. AT2s-KLF2-knockout or CEBPA AAV-knockdown mice nullified the GC-1 effect of anti-fibrosis and showed an abnormal regeneration in pneumonectomy, indicating that KLF2 and CEBPA are the anti-fibrotic targets of GC-1.