GSE113412
Tracking adipose-tissue Treg provenance, dependencies, and activities via T cell receptor transgenic mice
Regulatory T (Treg) cells located within parenchymal tissues safeguard tissue homeostasis. A paradigmatic "tissue-Treg" population is that found in visceral-adipose tissue (VAT) of male mice. VAT-Treg cells have a unique transcriptome, are clonally expanded, and promote metabolic health through effects on local immunocytes and adipocytes. Because of their rarity and inaccessibility, cardinal questions such as what factors control their accumulation in fat and when/where/how do they adopt their distinctive phenotype remained unanswered. We addressed these issues using VAT- Treg T-cell-receptor (TCR) transgenic mice. Accumulation of VAT-Tregs was driven by combined effects of TCR specificity, Foxp3 expression, and a cell-intrinsic response to interleukin-33. Their characteristic phenotype emerged in two stages: a minority of splenic Treg cells weakly up-regulated a slice of the VAT-Treg transcriptional signature, reflecting cell activation, but the definitive phenotype, arming cells for fat survival, was manifest only in VAT. This deeper understanding of tissue-Treg generation should facilitate precision-targeting strategies. Overall design: CD4+FOXP3+ Tregs were FACS-purified from thymus, spleen and visceral-adipose tissue and ATAC-seq (Assay for Transposase-Accessible Chromatin) was performed. The mouse strain is a novel VAT TCR transgenic (Tg) mouse line published in Li et al., (pending), called vTreg53. It was crossed with a FOXP3-reporter line containing an ires-GFP construct inserted into the FOXP3 locus, allowing FOXP3+ cells to be FACS-purified. In addition to standard T cell markers and FOXP3, Tregs from transgene-carrying mice were also purified as Valpha2-hi and Vbeta4-hi cells. Sample titles derived from mice carrying the TCR transgene are prepended with "TgP", for "Transgene-Positive", while samples derived from control, transgene-negative littermates are prepended with "TgN". Additionally, TCR transgene-carrying mice were crossed with a novel PPARg-reporter strain published in Li et al (pending). Two CD4+FOXP3+ Treg populations were purified from the spleens of these mice, as indicated by the sample titles: "SpPparNeg" are Pparg-negative Tregs and "SpPparLo" are Pparg-positive Tregs. "WO" in sample titles refers to "weeks-old", "Thy/Sp/VAT" refer to the Thymus, Spleen, or Visceral Adipose Tissue source and Rep* refers to biological replicate number.