Yazar "Benamar, Mehdi" seçeneğine göre listele

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    Single-cell analysis of FOXP3 deficiencies in humans and mice unmasks intrinsic and extrinsic CD4+ T cell perturbations
    (Nature Portfolio, 2021) Zemmour, David; Charbonnier, Louis-Marie; Leon, Juliette; Six, Emmanuelle; Keles, Sevgi; Delville, Marianne; Benamar, Mehdi
    FOXP3 deficiency in mice and in patients with immune dysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome results in fatal autoimmunity by altering regulatory T (T-reg) cells. CD4(+) T cells in patients with IPEX syndrome and Foxp3-deficient mice were analyzed by single-cell cytometry and RNA-sequencing, revealing heterogeneous T-reg-like cells, some very similar to normal T-reg cells, others more distant. Conventional T cells showed no widespread activation or helper T cell bias, but a monomorphic disease signature affected all CD4(+) T cells. This signature proved to be cell extrinsic since it was extinguished in mixed bone marrow chimeric mice and heterozygous mothers of patients with IPEX syndrome. Normal T-reg cells exerted dominant suppression, quenching the disease signature and revealing in mutant T-reg-like cells a small cluster of genes regulated cell-intrinsically by FOXP3, including key homeostatic regulators. We propose a two-step pathogenesis model: cell-intrinsic downregulation of core FOXP3-dependent genes destabilizes T-reg cells, de-repressing systemic mediators that imprint the disease signature on all T cells, furthering T-reg cell dysfunction. Accordingly, interleukin-2 treatment improved the T-reg-like compartment and survival. FOXP3 deficiency leads to dramatic loss of immune homeostasis. This multicenter collaborative group finds that loss of FOXP3 function only disrupts a few core genes, but this unmasks a degree of systemic inflammation, and it is this environment that then strongly perturbs T-reg cells.
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    A Stk4-Foxp3-NF-?B p65 transcriptional complex promotes Treg cell activation and homeostasis
    (Amer Assoc Advancement Science, 2022) Cui, Ye; Benamar, Mehdi; Schmitz-Abe, Klaus; Poondi-Krishnan, Varsha; Chen, Qian; Jugder, Bat-Erdene; Fatou, Benoit
    The molecular programs involved in regulatory T (T-reg) cell activation and homeostasis remain incompletely understood. Here, we show that T cell receptor (TCR) signaling in T-reg cells induces the nuclear translocation of serine/threonine kinase 4 (Stk4), leading to the formation of an Stk4-NF-kappa B p65-Foxp3 complex that regulates Foxp3- and p65-dependent transcriptional programs. This complex was stabilized by Stk4-dependent phosphorylation of Foxp3 on serine-418. Stk4 deficiency in T-reg cells, either alone or in combination with its homolog Stk3, precipitated a fatal autoimmune lymphoproliferative disease in mice characterized by decreased Treg cell p65 expression and nuclear translocation, impaired NF-kappa B p65-Foxp3 complex formation, and defective Treg cell activation. In an adoptive immunotherapy model, overexpression of p65 or the phosphomimetic Foxp3S418E in Stk3/4-deficient T-reg cells ameliorated their immune regulatory defects. Our studies identify Stk4 as an essential TCR-responsive regulator of p65-Foxp3-dependent transcription that promotes T-reg cellmediated immune tolerance.