The mammalian gastrointestinal tract harbors a microbial community with metabolic activity critical for host health, including metabolites that can modulate effector functions of immune cells. Mice treated with vancomycin have an altered microbiome and metabolite profile, exhibit exacerbated T helper type 2 cell (Th2) responses, and are more susceptible to allergic lung inflammation. Here we show that dietary supplementation with short-chain fatty acids (SCFAs) ameliorates this enhanced asthma susceptibility by modulating the activity of T cells and dendritic cells (DCs). Dysbiotic mice treated with SCFAs have fewer interleukin-4 (IL4)-producing CD4 T cells and decreased levels of circulating immunoglobulin E (IgE). In addition, DCs exposed to SCFAs activate T cells less robustly, are less motile in response to CCL19 in vitro, and exhibit a dampened ability to transport inhaled allergens to lung draining nodes. Our data thus demonstrate that gut dysbiosis can exacerbate allergic lung inflammation through both T cell- and DC-dependent mechanisms that are inhibited by SCFAs.

No abstract

The hematopoietic system produces a large number of highly specialized cell types that are derived through a hierarchical differentiation process from a common stem cell population. miRNAs are critical players in orchestrating this differentiation. Here, we report the development and application of a high-throughput microfluidic real-time quantitative PCR (RT-qPCR) approach for generating global miRNA profiles for 27 phenotypically distinct cell populations isolated from normal adult mouse hematopoietic tissues. A total of 80,000 RT-qPCR assays were used to map the landscape of miRNA expression across the hematopoietic hierarchy, including rare progenitor and stem cell populations. We show that miRNA profiles allow for the direct inference of cell lineage relations and functional similarity. Our analysis reveals a close relatedness of the miRNA expression patterns in multipotent progenitors and stem cells, followed by a major reprogramming upon restriction of differentiation potential to a single lineage. The analysis of miRNA expression in single hematopoietic cells further demonstrates that miRNA expression is very tightly regulated within highly purified populations, underscoring the potential of single-cell miRNA profiling for assessing compartment heterogeneity.RT-qPCR | stem cell | hematopoiesis | microfluidic | single cell

Methylation of nonhistone proteins is emerging as a regulatory mechanism to control protein function. Set7 (Setd7) is a SET-domain-containing lysine methyltransferase that methylates and alters function of a variety of proteins in vitro, but the in vivo relevance has not been established. We found that Set7 is a modifier of the Hippo pathway. Mice that lack Set7 have a larger progenitor compartment in the intestine, coinciding with increased expression of Yes-associated protein (Yap) target genes. Mechanistically, monomethylation of lysine 494 of Yap is critical for cytoplasmic retention. These results identify a methylation-dependent checkpoint in the Hippo pathway.

There is a great deal of interest in determining what regulates the generation of classically activated (M1) vs alternatively activated (M2) macrophages (Mφs) because of the opposing effects that these two Mφ subsets have on tumor progression. We show herein that IL-3 and, to a lesser extent, GM-CSF skew murine Mφ progenitors toward an M2 phenotype, especially in the absence of SHIP. Specifically, the addition of these cytokines, with or without M-CSF, to adherence- or lineage-depleted (Lin−) SHIP−/− bone marrow (BM) cells induces high levels of the M2 markers, arginase I, and Ym1 in the resulting mature Mφs. These in vitro-derived mature Mφs also display other M2 characteristics, including an inability to enhance anti-CD3-stimulated splenic T cell secretion of IFN-γ and low IL-12 and high IL-10 production in response to LPS. Not surprisingly, given that IL-3 and GM-CSF utilize STAT5 to trigger many downstream signaling pathways, this M2 phenotype is suppressed when STAT5−/− BM cells are used. Unexpectedly, however, this M2 phenotype is also suppressed when STAT6−/− BM cells are used, suggesting that IL-4- or IL-13-induced signaling might be involved. Consistent with this, we found that IL-3 and GM-CSF stimulate the production of IL-4, especially from SHIP−/− Lin− BM cells, and that neutralizing anti-IL-4 Abs block IL-3-induced M2 skewing. Moreover, we found that basophil progenitors within the Lin− BM are responsible for this IL-3- and GM-CSF-induced IL-4 production, and that SHIP represses M2 skewing not by preventing skewing within Mφs themselves but by inhibiting IL-4 production from basophils.