Embryonic stem (ES) cell self-renewal efficiency is determined by the Nanog protein level. However, the protein partners of Nanog that function to direct self-renewal are unclear. Here, we identify a Nanog interactome of over 130 proteins including transcription factors, chromatin modifying complexes, phosphorylation and ubiquitination enzymes, basal transcriptional machinery members, and RNA processing factors. Sox2 was identified as a robust interacting partner of Nanog. The purified Nanog–Sox2 complex identified a DNA recognition sequence present in multiple overlapping Nanog/Sox2 ChIP-Seq data sets. The Nanog tryptophan repeat region is necessary and sufficient for interaction with Sox2, with tryptophan residues required. In Sox2, tyrosine to alanine mutations within a triple-repeat motif (S X T/S Y) abrogates the Nanog–Sox2 interaction, alters expression of genes associated with the Nanog-Sox2 cognate sequence, and reduces the ability of Sox2 to rescue ES cell differentiation induced by endogenous Sox2 deletion. Substitution of the tyrosines with phenylalanine rescues both the Sox2–Nanog interaction and efficient self-renewal. These results suggest that aromatic stacking of Nanog tryptophans and Sox2 tyrosines mediates an interaction central to ES cell self-renewal.

Developmental defects affecting the heart and aortic arch arteries are a significant phenotype observed in individuals with 22q11 deletion syndrome and are caused by a microdeletion on chromosome 22q11. TBX1, one of the deleted genes, is expressed throughout the pharyngeal arches and is considered a key gene, when mutated, for the arch artery defects. Pax9 is expressed in the pharyngeal endoderm and is downregulated in Tbx1 mutant mice. We show here that Pax9-deficient mice are born with complex cardiovascular malformations that affect the outflow tract and aortic arch arteries with failure of the 3rd and 4th pharyngeal arch arteries to form correctly. Transcriptome analysis indicated that Pax9 and Tbx1 may function together, and mice double heterozygous for Tbx1/Pax9 presented with a significantly increased incidence of interrupted aortic arch when compared with Tbx1 heterozygous mice. Using a novel Pax9Cre allele, we demonstrated that the site of this Tbx1-Pax9 genetic interaction is the pharyngeal endoderm, therefore revealing that a Tbx1-Pax9-controlled signalling mechanism emanating from the pharyngeal endoderm is required for crucial tissue interactions during normal morphogenesis of the pharyngeal arch artery system.

Thymus function depends on the epithelial compartment of the thymic stroma. Cortical thymic epithelial cells (cTECs) regulate T cell lineage commitment and positive selection, while medullary (m) TECs impose central tolerance on the T cell repertoire. During thymus organogenesis, these functionally distinct sub-lineages are thought to arise from a common thymic epithelial progenitor cell (TEPC). However, the mechanisms controlling cTEC and mTEC production from the common TEPC are not understood. Here, we show that emergence of the earliest mTEC lineage-restricted progenitors requires active NOTCH signaling in progenitor TEC and that, once specified, further mTEC development is NOTCH independent. In addition, we demonstrate that persistent NOTCH activity favors maintenance of undifferentiated TEPCs at the expense of cTEC differentiation. Finally, we uncover a cross-regulatory relationship between NOTCH and FOXN1, a master regulator of TEC differentiation. These data establish NOTCH as a potent regulator of TEPC and mTEC fate during fetal thymus development, and are thus of high relevance to strategies aimed at generating/regenerating functional thymic tissue in vitro and in vivo.

Microbial diversity is associated with improved outcomes in recipients of allogeneic hematopoietic cell transplantation (allo-HCT), but the mechanism underlying this observation is unclear. In a cohort of 174 patients who underwent allo-HCT, we demonstrate that a diverse intestinal microbiome early after allo-HCT is associated with an increased number of innate-like mucosal-associated invariant T (MAIT) cells, which are in turn associated with improved overall survival and less acute graft-versus-host disease (aGVHD). Immune profiling of conventional and unconventional immune cell subsets revealed that the prevalence of Vδ2 cells, the major circulating subpopulation of γδ T cells, closely correlated with the frequency of MAIT cells and was associated with less aGVHD. Analysis of these populations using both single-cell transcriptomics and flow cytometry suggested a shift toward activated phenotypes and a gain of cytotoxic and effector functions after transplantation. A diverse intestinal microbiome with the capacity to produce activating ligands for MAIT and Vδ2 cells appeared to be necessary for the maintenance of these populations after allo-HCT. These data suggest an immunological link between intestinal microbial diversity, microbe-derived ligands, and maintenance of unconventional T cells.

GeneProf Data (http://www.geneprof.org) is an open web resource for analysed functional genomics experiments. We have built up a large collection of completely processed RNA-seq and ChIP-seq studies by carefully and transparently reanalysing and annotating high-profile public data sets. GeneProf makes these data instantly accessible in an easily interpretable, searchable and reusable manner and thus opens up the path to the advantages and insights gained from genome-scale experiments to a broader scientific audience. Moreover, GeneProf supports programmatic access to these data via web services to further facilitate the reuse of experimental data across tools and laboratories.

Developmental defects affecting the heart and aortic arch arteries are a key phenotype observed in DiGeorge syndrome patients and are caused by a microdeletion on chromosome 22q11. Heterozygosity of TBX1, one of the deleted genes, is expressed throughout the pharyngeal arches and is considered a key component for the arch artery defects. Pax9 is expressed in the pharyngeal endoderm and is downregulated in Tbx1 mutant mice. We show here that Pax9 deficient mice are born with complex cardiovascular malformations affecting the outflow tract and aortic arch arteries with failure of the 3rd and 4th pharyngeal arch arteries to form correctly. Transcriptome analysis indicated that Pax9 and Tbx1 may function together, and mice double heterozygous for Tbx1/Pax9 presented with a significantly increased incidence of interrupted aortic arch when compared to Tbx1 heterozygous mice. Using a novel Pax9Cre allele we demonstrated that the site of this Tbx1-Pax9 genetic interaction is in the pharyngeal endoderm, therefore revealing that a Tbx1/Pax9-controlled signalling mechanism emanating from the pharyngeal endoderm is required for critical tissue interactions during normal morphogenesis of the pharyngeal arch artery system.Summary statementPax9 is required for outflow tract and aortic arch development, and functions together with Tbx1 in the pharyngeal endoderm for 4th arch artery formation.

The intestinal microbiota is essential for the fermentation of dietary fiber into short-chain fatty acids (SCFA) such as butyrate, acetate, and propionate. SCFAs can bind to the G-protein-coupled receptors GPR43 and GPR109A (HCAR2), with varying affinities to promote cellular effects in metabolism or changes in immune function. We explored the role of GPR109A as the main receptor for butyrate in mouse models of allogeneic hematopoietic cell transplantation (allo-HCT) and graft-versus-host disease (GVHD). Deletion of GPR109A in allo-HCT recipients did not affect GVHD, but transplantation of T cells from GPR109A knockout (KO) (Gpr109a−/−) mice into allo-HCT recipient mice significantly reduced GVHD morbidity and mortality compared with recipients of wild-type (WT) T cells. Recipients of Gpr109a−/− T cells exhibited less GVHD-associated target organ pathology and decreased proliferation and homing of alloreactive T cells to target tissues. Although Gpr109a−/− T cells did not exhibit immune deficits at a steady state, following allo-activation, Gpr109a−/− T cells underwent increased apoptosis and were impaired mitochondrial oxidative phosphorylation, which was reversible through antioxidant treatment with N-acetylcysteine (NAC). In conclusion, we found that GPR109A expression by allo-activated T cells is essential for metabolic homeostasis and expansion, which are necessary features to induce GVHD after allo-HCT.

SUMMARYThe thymus, the primary site of T cell development, is extremely sensitive to insult but also harbors tremendous capacity for repair. Using single cell sequencing of thymic structural cells, as well as functional and structural analyses, we revealed distinct regenerative programs by endothelial and mesenchymal subsets after injury that stimulated epithelial repair; the compartment primarily supporting T cell development. Thymic function not only declined over lifespan, contributing to immune aging, but the capacity of the thymus to regenerate after damage also declined in old mice. This could be attributed to an inability of the old microenvironment to induce reparative programs; leading to reduced ability to restore tissue structure and function. These findings provide a detailed framework for the response of structural cells to aging and acute damage, which could have considerable implications for our understanding of aging immunity and recovery from treatments such as chemotherapy and bone marrow transplant.