A generic level of chromatin organization generated by the interplay between cohesin and CTCF suffices to limit promiscuous interactions between regulatory elements, but a lineage-specific chromatin assembly that supersedes these constraints is required to configure the genome to guide gene expression changes that drive faithful lineage progression. Loss-of-function approaches in B cell precursors show that IKAROS assembles interactions across megabase distances in preparation for lymphoid development. Interactions emanating from IKAROS-bound enhancers override CTCF-imposed boundaries to assemble lineage-specific regulatory units built on a backbone of smaller invariant topological domains. Gain of function in epithelial cells confirms IKAROS' ability to reconfigure chromatin architecture at multiple scales. Although the compaction of the Igκ locus required for genome editing represents a function of IKAROS unique to lymphocytes, the more general function to preconfigure the genome to support lineage-specific gene expression and suppress activation of extra-lineage genes provides a paradigm for lineage restriction.
Published by Elsevier Inc.

Cub domain-containing protein 1 (CDCP1) is a protein that is highly expressed on the surface of many cancer cells. However, its distribution in normal tissues and its potential roles in nontumor cells are poorly understood. We found that CDCP1 is present on both human and mouse retinal pigment epithelial (RPE) cells. CDCP1-KO mice developed attenuated retinal inflammation in a passive model of autoimmune uveitis, with disrupted tight junctions and infiltrating T cells detected in RPE flat mounts from WT but not CDCP1-KO mice during EAU development. Mechanistically, we discovered that CDCP1 on RPE cells was upregulated by IFN-γ in vitro and after EAU induction in vivo. CD6 stimulation induced increased RPE barrier permeability of WT but not CDCP1-knockdown (CDCP1-KD) RPE cells, and activated T cells migrated through WT RPE monolayers more efficiently than the CDCP1-KD RPE monolayers. In addition, CD6 stimulation of WT but not the CDCP1-KD RPE cells induced massive stress fiber formation and focal adhesion disruption to reduce cell barrier tight junctions. These data suggest that CDCP1 on RPE cells interacts with CD6 on T cells to induce RPE cytoskeleton remodeling and focal adhesion disruption, which open up the tight junctions to facilitate T cell infiltration for the development of uveitis.

Effector CD8 + T cell interactions are critical in controlling viral infection by directly killing infected cells but overabundant or sustained activation also exacerbates tissue damage. Chemokines promote the trafficking of effector CD8 + T cells into infected tissues, but we know little about how chemokines regulate the function of CD8 + T cells within tissues. Using a murine model of influenza A virus infection, we found that expression of the chemokine receptor CXCR4 by lung-infiltrating cytotoxic T cells correlated with the expression of the degranulation marker CD107a. Inhibition of CXCR4 reduced activation, adhesion, and degranulation of cytotoxic T cells in vitro and in vivo . Moreover, in live influenza-infected lung tissue, T cells stopped moving in lung regions with high levels of influenza antigen, and CXCR4 was essential for CD8 + T cells to execute this arrest signal fully. In contrast, CXCR4 increased the motility of CD8 + T cells in low-influenza areas of the lung. We also found that CXCR4 stimulated the effector function of lung-infiltrating cytotoxic T cells even after clearance of influenza virus, and inhibition of CXCR4 expedited the recovery of influenza-infected mice, despite delayed clearance of the replication-competent virus. Our results suggest that CXCR4 promotes the interaction strength of cytotoxic T cells in lung tissue through combined effects on T cell movement and interaction with virally infected target cells in influenza infected-lungs.

Although microbe-associated molecular pattern (MAMP) molecules can promote cholesterol accumulation in macrophages, the existence of a host-derived MAMP inactivation mechanism that prevents foam cell formation has not been described. Here, we tested the ability of acyloxyacyl hydrolase (AOAH), the host lipase that inactivates gram-negative bacterial lipopolysaccharides (LPSs), to prevent foam cell formation in mice. Following exposure to small intraperitoneal dose(s) of LPSs, Aoah -/- macrophages produced more low-density lipoprotein receptor and less apolipoprotein E and accumulated more cholesterol than did Aoah +/+ macrophages. The Aoah -/- macrophages also maintained several pro-inflammatory features. Using a perivascular collar placement model, we found that Aoah -/- mice developed more carotid artery foam cells than did Aoah +/+ mice after they had been fed a high fat, high cholesterol diet, and received small doses of LPSs. This is the first demonstration that an enzyme that inactivates a stimulatory MAMP in vivo can reduce cholesterol accumulation and inflammation in arterial macrophages.
© 2021 The Authors.

Lack or dysfunction of the lymphatics leads to secondary lymphedema formation that seriously reduces the function of the affected organs and results in degradation of quality of life. Currently, there is no definitive treatment option for lymphedema. Here, we utilized nucleoside-modified mRNA encapsulated in lipid nanoparticles (LNPs) encoding murine Vascular Endothelial Growth Factor C (VEGFC) to stimulate lymphatic growth and function and reduce experimental lymphedema in mouse models. We demonstrated that administration of a single low-dose of VEGFC mRNA-LNPs induced durable, organ-specific lymphatic growth and formation of a functional lymphatic network. Importantly, VEGFC mRNA-LNP treatment reversed experimental lymphedema by restoring lymphatic function without inducing any obvious adverse events. Collectively, we present a novel application of the nucleoside-modified mRNA-LNP platform, describe a model for identifying the organ-specific physiological and pathophysiological roles of the lymphatics, and propose an efficient and safe treatment option that may serve as a novel therapeutic tool to reduce lymphedema.