Biology subjects

Hayer, K.

Publications and source records attributed to Hayer, K..

5 recordsLinked to original sources

bioRxiv2025

E2f coordinates the proliferation and transdifferentiation of a Sox9+bile duct cell to initiate hepatocellular carcinoma

Disruption of the Rb/E2f interaction is one of the six original hallmarks of cancer and is thought to confer unrestricted proliferative potential to tumor cells. Although E2f is active in almost all cancer cases as a result of this disruption, the consequence of its unrestricted activity for cancer initiation remains mostly unknown. To address this question, we genetically inactivated the entire Rb family of genes (Triple Knock Out, TKO) in specific cell lineages in the liver. Strikingly, this unbiased approach reveals that Rb family inactivation initiates a phenotypically similar hepatocellular carcinoma (HCC) from either periportal hepatocytes or Sox9+ bile duct cells. In the latter population, Rb family inactivation results in unrestricted proliferation as well as the E2f-driven transactivation of the pioneer factor Foxa3, which activates a "periportal hepatocyte-like" metabolic program to ensure transdifferentiation into hepatocytes. Notably, single or compound inactivation of E2f1 and E2f3 in the TKO background is sufficient to suppress Foxa3 expression and HCC initiation, without altering the proliferative status of Sox9+ bile duct cells. Collectively, our results reveal that derepression of a cell cycle gene program and activation of non-cell cycle oncogenic features by E2f are distinct consequences of disrupting the Rb/E2f interaction, and that coordinated activation of these two functions are essential for HCC initiation from a founder liver bile duct cell lineage.

cancer biology↗

bioRxiv2025

E2f coordinates the cell cycle and cell fate of hematopoietic progenitors to drive stress myelopoiesis

During inflammation, cytokines such as Tnf, Il1{beta} and Il6 stimulate hematopoietic stem and progenitor cells (HSPCs) to proliferate and accelerate the production of inflammatory cells from the myeloid lineage through a process called stress myelopoiesis. Genetic inactivation of repressors of cell cycle activity in HSPCs is sufficient to recapitulate stress myelopoiesis, suggesting that the cell cycle activity and cell fate decision of proliferative HSPCs are coordinated by a cell intrinsic mechanism. However, the nature of this mechanism remains unknown. Here, we show that E2f simultaneously regulates proliferation of HSPCs, repression of alternative cell fates via the activation of Suz12/Ezh2-containing PRC2 complex and promotion of the myeloid fate by enhancing the signaling activity of CD131, the common {beta}chain receptor for {beta}cytokines (i.e. Il3 and Gm-Csf). Accordingly, dual inhibition of Ezh2 and {beta}cytokine signaling activity in a preclinical model of colitis represses stress myelopoiesis and restores colon homeostasis. Our results suggest that dual targeting of {beta}cytokine signaling and Ezh2 activity represents a novel therapeutic strategy to repress the production of pro-inflammatory myeloid cells in a wide spectrum of inflammatory diseases.

cell biology↗

bioRxiv2024

Promoter- and Enhancer-Dependent Cohesin Loading Initiates Chromosome Looping to Fold Tcrb Loci for Long-Range Recombination

Cohesin-mediated chromosome looping regulates diverse processes, including antigen receptor (AgR) gene assembly by V(D)J recombination. To understand mechanisms that coordinate genome topologies, we focused on a genetically tractable AgR locus, Tcrb. Cohesin loading and initiating loop extrusion (LE) from a nearby CTCF-binding element (CBE) required the promoter of the most 5V{beta} segment, creating long-range contacts with target downstream DJ{beta} segments within the recombination center (RC). CBEs flanking the RC have multiple functions: terminators of LE originating in the V{beta} cluster, initiators of LE in the RC, and insulation of enhancer activity. Deletion of the Tcrb super-enhancer abolished loop extrusion from the neighboring RC but spared long-range contacts, indicating that unidirectional loop extrusion from upstream V{beta} segments was sufficient. Thus, V{beta} promoter- or enhancer-dependent cohesin loading initiates LE in opposite directions across the locus to assemble a broad Tcrb repertoire, a finding that has broad implications for genomic architecture and function.

molecular biology↗

bioRxiv2021

The RAG1 Ubiquitin Ligase Domain Enhances T Cell Receptor Gene Assembly and Thymic Selection

RAG1/RAG2 (RAG) endonuclease-mediated assembly of diverse lymphocyte antigen receptor genes by V(D)J recombination is critical for the development and immune function of T and B cells. However, this process creates highly self-reactive cells that must be properly selected to suppress autoimmunity. The RAG1 protein contains a ubiquitin ligase domain that stabilizes RAG1 and stimulates RAG endonuclease activity in vitro. We report that mice with a mutation that inactivates the RAG1 ubiquitin ligase in vitro exhibit modestly reduced thymic cellularity, decreased assembly and altered repertoires of T cell receptor (TCR) {beta} and genes in thymocytes, and impaired thymocyte developmental transitions that require the assembly of TCR{beta} or genes and signaling by their proteins. These RAG1 mutant mice also exhibit less efficient positive selection and superantigen-mediated negative selection of conventional {beta} T cells, 2) impaired differentiation of iNKT lineage {beta} T cells, and 3) CD4+ {beta} T cells with elevated autoimmune potential. Our findings demonstrate that the RAG1 ubiquitin ligase domain functions in vivo to stimulate the assembly and selection of TCR{beta} and TCR genes, thereby establishing replete diversity of {beta} TCRs and {beta} T cell lineages while restraining the inherent autoimmune hazard of generating diverse antigen specificities.

immunology↗

bioRxiv2019

Impaired tumor death receptor signaling drives resistance to CAR T cell therapy

Cellular immunotherapy using T cells engineered to express chimeric antigen receptors targeting CD19 (CART19) leads to long-term remission in patients with B-cell malignancies1-5. Unfortunately, a significant fraction of patients demonstrate primary resistance to CART19 or experience relapse after achieving remission. Beyond loss of target antigen, the molecular pathways governing CART19 failure are unknown. Here we demonstrate that death receptors, cell surface signaling molecules that induce target cell apoptosis, are key mediators of leukemic resistance and CART19 failure. Using a functional CRISPR/Cas9-based genome-wide knockout screen6 in B-cell acute lymphoblastic leukemia (ALL), we identified the death receptor signaling pathway as a central regulator of sensitivity to CART19-induced cell death. In the absence of the pro-apoptotic death receptor signaling molecules BID or FADD, ALL cells were resistant to CART19 cytotoxicity, resulting in rapid disease progression in mice. We found that this initial resistance to cytotoxicity led to persistence of tumor cells, which drove the development of T cell dysfunction that further compromised anti-tumor immunity and permitted tumor outgrowth. We validated these findings using clinical samples collected from patients with ALL treated with CD19-targeted CAR T cells and found that expression of pro-apoptotic death receptor pathway genes in pre-treatment tumor samples correlated with CAR T cell expansion and persistence, as well as patient response and overall survival. Our findings indicate that tumor-intrinsic death receptor signaling directly contributes to CAR T cell failure.

immunology↗