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The aryl hydrocarbon receptor binds to kynurenine and mediates a signal supports the undifferentiated state in pluripotent stem cells

ABSTRACT: Kynurenine is generated from tryptophan by indoleamine 2,3-dioxygenase (IDO1) and binds to the aryl hydrocarbon receptor (AhR). We found that kynurenine generated by human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) stimulated the AhR to bind selectively to the promoters and enhancers of self-renewal genes, thus enhancing their transcription. The kynurenine-AhR complex also directly stimulated the expression of IDO1 and AHR, activating a positive feedback loop. Substantial amounts of kynurenine that were not complexed with AhR were present in the culture medium, providing a paracrine signal for maintenance of the undifferentiated state. Kynurenine was not present in the medium of differentiated ESCs and iPSCs. When cells were induced to undergo ectodermal differentiation, the abundance of kynurenine in the medium was reduced through activation of the main kynurenine catabolic pathway mediated by aminotransferase 2 (KAT2), resulting in the secretion of 2-aminoadipic acid (2-AAA) into the culture medium. Thus, kynurenine in the culture medium is a biomarker for the undifferentiated state, and 2-AAA in the culture medium is a biomarker for ESCs and iPSCs that have committed to differentiate along the ectoderm lineage.

ORGANISM(S): Homo sapiens

PROVIDER: GSE129507 | GEO | 2019/06/09

REPOSITORIES: GEO

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Project description:Understanding the mechanisms of host macrophage responses to M. tuberculosis (M.tb.) is essential for uncovering potential avenues of intervention to boost host resistance to infection. Macrophage transcriptome profiling revealed M.tb. infection strongly induced expression of several enzymes controlling tryptophan (Trp) catabolism. This included indole 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO2), which catalyze the rate-limiting step in the kynurenine pathway, producing ligands for the aryl hydrocarbon receptor (AHR). The AHR and heterodimeric partners AHR nuclear translocator (ARNT) and RELB are robustly expressed, and AHR and RELB levels further increased during infection. Infection enhanced AHR/ARNT and AHR/RELB DNA binding, and stimulated expression of AHR target genes, including that encoding the inflammatory cytokine IL1beta. AHR target gene expression was further enhanced by exogenous kynurenine, and exogenous Trp, kynurenine or synthetic agonist indirubin reduced mycobacterial viability. Comparative expression profiling revealed that AHR ablation diminished expression of numerous genes implicated in innate immune responses, including several cytokines. Notably, AHR depletion reduced expression of IL23A and IL12B transcripts, which encode subunits of interleukin 23 (IL23), a macrophage cytokine that stimulates production of IL22 by innate lymphoid cells. The AHR directly induced IL23A transcription in human and mouse macrophages through near-upstream enhancer regions. Taken together, these findings show that AHR signaling is strongly engaged in Mtb-infected macrophages, and has widespread effects on innate immune responses. Moreover, they reveal a cascade of AHR-driven innate immune signaling, as IL1B (IL-1β) and IL23 stimulate T cell subsets producing IL22, another direct target of AHR transactivation. Gene expression profiling of Mtb-infected THP-1 monocytic cells following siRNA-mediated Aryl hydrocarbon receptor (AHR) knockdown.

Project description:Derivation and maintenance of pluripotent stem cells (PSCs) including embryonic stem cells(ESCs) and (iPSCs) usually requires optimization of complex culture media, which hinders the generation of PSCs from various species. Expression of Oct4, Sox2, Klf4 and c-Myc (OSKM) can reprogram somatic cells into iPSCs, even for species possessing no optimal culture condition. Here we explored whether expression of OSKM could induce and maintain pluripotency without specific growth factors and signaling inhibitors. Tet-On-OSKM/Oct4-GFP Mouse ESCs (mESCs) were derived from the embryos obtained after mating of Tet-On-OSKM mouse and Oct4-GFP mouse under the 2iL ( N2B27 plus MEK inhibitor PD0325901, GSK3β inhibitor ChIR99021, and leukemia inhibitory factor) condition. Tet-On-OSKM mouse was Gt(ROSA)26Sor tm1(rtTA*M2)Jae Col1a1 tm3(tetO-Pou5f1,-Sox2,-Klf4,-Myc)Jae/J(The Jackson Laboratory,011004), and Oct4-GFP mouse was B6;CBA-Tg(Pou5f1-EGFP)2Mnn/J (The Jackson Laboratory,004654).The culture medium of Tet-On-OSKM/Oct4-GFP mouse ESCs was switched from 2iL to N2B27 plus Doxycycline medium (OSKM medium), under which OSKM trangene was activated. These above cells switched from 2iL to OSKM medium were called OSKM-ESCs. Meanwhile 2iL-ESCs (continuely cultured in 2iL) served as the positive control group. 2iL-ESCs and OSKM-ESCs collected at selective days (d18, 25 and 38) after medium switch were collected for RNA-Seq. Moreover, Tet-On-OSKM mouse embryonic fibroblast (MEF) cells were reprogrammed under OSKM medium (N2B27 plus Doxycycline) and 2iL medium, respectively. The resulting OSKM-iPSCs were reprogrammed and cultured under OSKM medium.The 2iL-iPSCs were reprogrammed under 2iL plus Doxycycline medium and cultured under 2iL medium (without Doxycycline)once clones were picked up.RNA-Seq of these above samples was conducted to analyze gene expression. We found that via continuous expression of OSKM,OSKM-ESCs and OSKM-iPSCs propagated stably, expressed pluripotency marker genes, and formed three germ layers in teratomas. Importantly, OSKM-iPSCs could produce gene-modified animals through germline transmission.Transcriptional landscapes of OSKM-iPSCs resembled 2iL-ESCs, and were more similar to those of ESCs cultured in serum/LIF.

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The aryl hydrocarbon receptor binds to kynurenine and mediates a signal supports the undifferentiated state in pluripotent stem cells

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