Deficiency of the Metalloproteinase-Disintegrin ADAM8 Is Associated with Thymic Hyper-Cellularity

Thymopoiesis requires thymocyte-stroma interactions and proteases that promote cell migration by degrading extracellular matrix and releasing essential cytokines and chemokines. A role for several members of the A Disintegrin and Metalloprotease (ADAM) family in T cell development has been reported in the past

Trim28 Haploinsufficiency Triggers Bi-stable Epigenetic Obesity.

This is the final version of the article. It first appeared from Cell Press via http://dx.doi.org/10.1016/j.cell.2015.12.025More than one-half billion people are obese, and despite progress in genetic research, much of the heritability of obesity remains enigmatic. Here, we identify a Trim28-dependent network capable of triggering obesity in a non-Mendelian, "on/off" manner. Trim28(+/D9) mutant mice exhibit a bi-modal body-weight distribution, with isogenic animals randomly emerging as either normal or obese and few intermediates. We find that the obese-"on" state is characterized by reduced expression of an imprinted gene network including Nnat, Peg3, Cdkn1c, and Plagl1 and that independent targeting of these alleles recapitulates the stochastic bi-stable disease phenotype. Adipose tissue transcriptome analyses in children indicate that humans too cluster into distinct sub-populations, stratifying according to Trim28 expression, transcriptome organization, and obesity-associated imprinted gene dysregulation. These data provide evidence of discrete polyphenism in mouse and man and thus carry important implications for complex trait genetics, evolution, and medicine.This work was supported by funding from the Max-Planck Society, ERC (ERC-StG-281641), DFG (SFB992 “MedEp”; SFB 1052 “ObesityMechanisms”), EU_FP7 (NoE ”Epigenesys”; “Beta-JUDO” n° 279153), BMBF (DEEP), MRC (Metabolic Disease Unit - APC, SOR, GSHY, MRC_MC_UU_12012/1), Wellcome Trust (SOR, 095515/Z/11/Z) and the German Research Council (DFG) for the Clinical Research Center "Obesity Mechanisms" CRC1052/1 C05 and the Federal Ministry of Education and Research, Germany, FKZ, 01EO1001 (Integrated Research and Treatment Center (IFB) Adiposity Diseases

Thymic progenitor homing and lymphocyte homeostasis are linked via S1P-controlled expression of thymic P-selectin/CCL25

Thymic T cell progenitor (TCP) importation is a periodic, gated event that is dependent on the expression of functional P-selectin ligands on TCPs. Occupancy of intrathymic TCP niches is believed to negatively regulate TCP importation, but the nature of this feedback mechanism is not yet resolved. We show that P-selectin and CCL25 are periodically expressed in the thymus and are essential parts of the thymic gate-keeping mechanism. Periodicity of thymic TCP receptivity and the size of the earliest intrathymic TCP pool were dependent on the presence of functional P-selectin ligand on TCPs. Furthermore, we show that the numbers of peripheral blood lymphocytes directly affected thymic P-selectin expression and TCP receptivity. We identified sphingosine-1-phosphate (S1P) as one feedback signal that could mediate influence of the peripheral lymphocyte pool on thymic TCP receptivity. Our findings suggest a model whereby thymic TCP importation is controlled by both early thymic niche occupancy and the peripheral lymphocyte pool via S1P

Regulation of thymic T cell progenitor importation

The thymus does not contain self-renewing T cell progenitors (TCP) and therefore requires continuous importation of progenitors from the blood to sustain T cell production. Recruitment of TCP to the thymus is facilitated by a multistep adhesion cascade initiated by the interaction of PSGL-1 expressed on TCP with P-selectin expressed on thymic endothelium. Thymic TCP importation is not a steady state process but is a periodic, gated event thought to be regulated by a negative feedback signal dependent on the occupation status of intrathymic TCP niches. However the nature of this feedback mechanism remains enigmatic. The aim of this study is to analyze the underlying mechanism that control thymic TCP importation in a temporal and quantitative manner. The study is based on the hypothesis that ingress of TCP into the thymus is controlled by the regulated expression of key molecules within the thymic adhesion cascade. Indeed, the first set of data shows that Pselectin and CCL25 expression correlate with thymic receptivity. Furthermore, this study finds that P-selectin and CCL25 are periodically expressed in thymic tissues indicating that they are essential parts of the thymic gate-keeping-mechanism. Absence of the P-selectin on thymic endothelial cells or functional P-selectin ligands on TCP significantly reduces the numbers of the earliest intrathymic TCP population and abolishes periodic expression of Pselectin and CCL25 suggesting that niche occupancy plays a role in regulating the periodicity of thymic TCP importation. The study further shows that the size of the peripheral lymphocyte pool directly affects thymic P-selectin expression and TCP receptivity indicating that extrathymic factors also control thymic receptivity. As a feedback signal that could mediate changes in the peripheral lymphocyte pool into altered thymic TCP receptivity sphingosine-1-phosphate (S1P) was identified. These findings suggest a model whereby thymic TCP importation is controlled by both early thymic niche occupancy and the peripheral lymphocyte pool via S1P.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat

Hepatic Cholesterol-25-Hydroxylase Overexpression Improves Systemic Insulin Sensitivity in Mice

Obesity is a major risk factor for several diseases including diabetes, heart disease, and some forms of cancer and due to its rapidly increasing prevalence it has become one of the biggest problems medicine is facing today. All the more surprising, a substantial percentage of obese patients are metabolically healthy when classified based on insulin resistance and systemic inflammation. Oxysterols are naturally occurring molecules that play important role in various metabolic and inflammatory processes and their levels are elevated in patients suffering from obesity and diabetes. 25-Hydroxycholesterol (25-OHC) is produced in cells from cholesterol by the enzyme cholesterol 25-hydroxylase (Ch25h) and is involved in lipid metabolism, inflammatory processes, and cell proliferation. Here, we investigated the role of hepatic Ch25h in the transition from metabolically healthy obesity to insulin resistance and diabetes. Using several different experimental approaches, we demonstrated the significance of Ch25h on the border of “healthy” and “diseased” states of obesity. Adenovirus-mediated Ch25h overexpression in mice improved glucose tolerance and insulin sensitivity and lowered HOMA-IR. Our data suggest that low hepatic Ch25h levels could be considered a risk marker for unhealthy obesity.(VLID)486245

ADAM8^−/− thymocytes have increased proliferation and reduced apoptosis rates.

<p>(A) Frequencies of Ki-67^hi cells in DN, DP^lo and DP^hi subsets of wt and ADAM8^−/− thymi. (B) Frequency of Caspase-3⁺ thymocytes in wt and ADAM8^−/− thymi. Data are representative of two independent experiments with n≥4 age- and gender-matched mice per group in each experiment. Data are presented as mean values and error bars as SEM. *, p<0.05, **, p<0.01.</p

ADAM8^−/− thymi have an increased mass and a reduced cortex/medulla ratio associated with a relative increase in mTEC.

<p>(A) Weight and (B) total numbers of thymocytes thymi from age- and gender-matched wt and ADAM^−/− mice (n = 8). (C) Cortex/medulla ratios examined on Hematoxylin/Eosin stained 20 µm sections of wt and ADAM8^−/− thymi (each 6 sections of 6 wt or ADAM^−/− thymi). Frequencies of (D) cTEC (Ly51^hi, UEA-1^lo) and (E) mTEC (Ly51^lo, UEA-1^hi) in CD45⁻, EpCAM⁺ thymic epithelial fraction of thymic suspensions obtained by collagenase/dispase treatment. Data are representative of two independent experiments with at least four mice per group. Data are presented as mean values and error bars as SEM. *, p<0.05, **, p<0.01, *** p<0.001.</p

ADAM8 is expressed in thymic stromal cells and thymocytes.

<p>Relative ADAM8 RNA levels as determined by qrtPCR in (A) total thymic tissue, thymic hematopoietic cells (CD45⁺, EpCAM⁻), epithelial cells (CD45⁻, EpCAM⁺), endothelial cells (CD45⁻, EpCAM⁻, CD31⁺) and other non-epithelial stromal cells (EpCAM⁻, CD45⁻, CD31⁻), (B) thymic T cell subsets and (C) TEC. FACS sorted cells (>95% purity) were analyzed for ADAM8 RNA expression using the reference gene HPRT. ADAM8 RNA values are expressed relative to HPRT expression. Data are presented as mean values and error bars as SEM. Data are from at least two independent experiments (n≥3). (D–G) Reporter gene (β-galactosidase) expression in ADAM8^−/− thymic sections detected by immunofluorescence. Thymic sections were stained with antibodies directed against β-galactosidase to reveal potential ADAM8 expression and (D) β5t marking cTEC, (E) MTS10 marking mTEC, (F) ER-TR7 marking fibroblasts and (G) KT-3 marking T cells. Scales bar 50 µm. Data are from at least four independent experiments (n≥4).</p