ABSTRACT X Chromosome Inactivation (XCI) is a female-specific process which balances X-linked gene dosage between sexes. Unstimulated T cells lack cytological enrichment of Xist RNA and heterochromatic modifications on the inactive X chromosome (Xi), and these modifications become enriched at the Xi after cell stimulation. Here, we examined allele-specific gene expression and the epigenomic profiles of the Xi following T cell stimulation. We found that the Xi in unstimulated T cells is largely dosage compensated and is enriched with the repressive H3K27me3 modification, but not the H2AK119-ubiquitin (Ub) mark, even at promoters of XCI escape genes. Upon CD3/CD28-mediated T cell stimulation, the Xi accumulates H2AK119-Ub and H3K27me3 across the Xi. Next, we examined the T cell signaling pathways responsible for Xist RNA localization to the Xi and found that T cell receptor (TCR) engagement, specifically NF-κB signaling downstream of TCR, is required. Disruption of NF-κB signaling, using inhibitors or genetic deletions, in mice and patients with immunodeficiencies prevents Xist/XIST RNA accumulation at the Xi and alters expression of some X-linked genes. Our findings reveal a novel connection between NF-κB signaling pathways which impact XCI maintenance in female T cells.
Purpose Regulatory T (Treg) cells are an essential subset of CD4+ T cells that induce and maintain immunological tolerance. Preclinical animal models have demonstrated that adoptive transfer of Treg cells can prevent or cure diabetes, multiple sclerosis (EAE), inflammatory bowel disease, lupus, arthritis, and graft versus host disease. Defects in Treg cell function and number have been described in a number of different human autoimmune diseases including diabetes, multiple sclerosis, rheumatoid arthritis and juvenile idiopathic arthritis. These data suggest that manipulation of Treg cells may be a useful therapeutic intervention. Treg cells are marked by expression of the forkhead/winged helix transcription factor Foxp3, which is essential for their regulatory functions. Treg cells are well known to mediate their immunomodulatory effects through TGF-b, IL-10 and CTLA-4. Recent work has also suggested a role for the granule/exocytosis pathway in Treg cell suppressive function. Granzyme A and granzyme B (gzm A and gzm B, respectively) mRNAs are expressed at high levels in Treg cells, and Treg cells from gzm B–/– mice showed defects in suppression in vitro. To further examine the role of granzymes in the function of Treg cells in vivo, we used a T cell transfer model of colitis. In this model, naive CD45RBhigh CD4+ T cells transferred to RAG–/– mice and undergo homeostatic expansion and activation.This process results in colitis manifested clinically by weight loss and shortened survival. Previous work has shown that a subset of the transferred conventional T cells develop into Foxp3+ iTreg cells and that these iTreg cells are necessary to mitigate colitis when present together with natural Treg cells (nTreg) cells derived in the thymus. Methods CD45RBhigh T cells from mice expressing a Foxp3EGFP fusion protein and additionally deficient in gzm A or gzm B are transferred to RAG-/mice.In these mice, EGFP expression marks iTreg which have developed in situ. Mice were weighed twice weekly and euthanized when moribund or when they have lost more than 1520% of their initial weight. Mesenteric lymph nodes T cells were analyzed for expression of EGFP.
Systemic juvenile idiopathic arthritis (sJIA) is an often severe, potentially life-threatening childhood inflammatory disease, the pathophysiology of which is poorly understood. To determine whether genetic variation within the MHC locus on chromosome 6 influences sJIA susceptibility, we performed an association study of 982 children with sJIA and 8,010 healthy control subjects from nine countries. Using meta-analysis of directly observed and imputed SNP genotypes and imputed classic HLA types, we identified the MHC locus as a bona fide susceptibility locus with effects on sJIA risk that transcended geographically defined strata. The strongest sJIA-associated SNP, rs151043342 [P = 2.8 × 10(-17), odds ratio (OR) 2.6 (2.1, 3.3)], was part of a cluster of 482 sJIA-associated SNPs that spanned a 400-kb region and included the class II HLA region. Conditional analysis controlling for the effect of rs151043342 found that rs12722051 independently influenced sJIA risk [P = 1.0 × 10(-5), OR 0.7 (0.6, 0.8)]. Meta-analysis of imputed classic HLA-type associations in six study populations of Western European ancestry revealed that HLA-DRB1*11 and its defining amino acid residue, glutamate 58, were strongly associated with sJIA [P = 2.7 × 10(-16), OR 2.3 (1.9, 2.8)], as was the HLA-DRB1*11-HLA-DQA1*05-HLA-DQB1*03 haplotype [6.4 × 10(-17), OR 2.3 (1.9, 2.9)]. By examining the MHC locus in the largest collection of sJIA patients assembled to date, this study solidifies the relationship between the class II HLA region and sJIA, implicating adaptive immune molecules in the pathogenesis of sJIA.
The early diagnosis and treatment of inborn errors of immunity (IEI) is crucial in reducing the morbidity and mortality due to these disorders. The institution of newborn screening (NBS) for the diagnosis of Severe Combined Immune Deficiency (SCID) has decreased the mortality of this disorder and led to the discovery of novel genetic defects that cause this disease. GATA2 deficiency is an autosomal dominant, pleiotropic disease with clinical manifestations that include bone marrow failure, monocyte and B cell deficiency, leukemia, pulmonary alveolar proteinosis and lymphedema. We present the case of an infant identified by newborn screening for SCID due to GATA2 deficiency.
