A central role for STAT5 in the transcriptional programing of T helper cell metabolism

Activated lymphocytes adapt their metabolism to meet the energetic and biosynthetic demands imposed by rapid growth and proliferation. Common gamma chain (cγ) family cytokines are central to these processes, but the role of downstream signal transducer and activator of transcription 5 (STAT5) signaling, which is engaged by all cγ members, is poorly understood. Using genome-, transcriptome-, and metabolome-wide analyses, we demonstrate that STAT5 is a master regulator of energy and amino acid metabolism in CD4⁺ T helper cells. Mechanistically, STAT5 localizes to an array of enhancers and promoters for genes encoding essential enzymes and transporters, where it facilitates p300 recruitment and epigenetic remodeling. We also find that STAT5 licenses the activity of two other key metabolic regulators, the mTOR signaling pathway and the MYC transcription factor. Building on the latter, we present evidence for transcriptome-wide cooperation between STAT5 and MYC in both normal and transformed T cells. Together, our data provide a molecular framework for transcriptional programing of T cell metabolism downstream of cγ cytokines and highlight the JAK-STAT pathway in mediating cellular growth and proliferation.

BACH2 immunodeficiency illustrates an association between super-enhancers and haploinsufficiency

The transcriptional programs that guide lymphocyte differentiation depend on the precise expression and timing of transcription factors (TFs). The TF BACH2 is essential for T and B lymphocytes and is associated with an archetypal super-enhancer (SE). Single-nucleotide variants in the BACH2 locus are associated with several autoimmune diseases, but BACH2 mutations that cause Mendelian monogenic primary immunodeficiency have not previously been identified. Here we describe a syndrome of BACH2-related immunodeficiency and autoimmunity (BRIDA) that results from BACH2 haploinsufficiency. Affected subjects had lymphocyte-maturation defects that caused immunoglobulin deficiency and intestinal inflammation. The mutations disrupted protein stability by interfering with homodimerization or by causing aggregation. We observed analogous lymphocyte defects in Bach2-heterozygous mice. More generally, we observed that genes that cause monogenic haploinsufficient diseases were substantially enriched for TFs and SE architecture. These findings reveal a previously unrecognized feature of SE architecture in Mendelian diseases of immunity: heterozygous mutations in SE-regulated genes identified by whole-exome/genome sequencing may have greater significance than previously recognized.

Elevated erythrocyte CDP-choline levels associated with beta-thalassaemia in patients with transfusion independent anaemia

The accumulation of CDP-ethanolamine as well as CDP-choline in a small cohort of patients with normal UMPH1 and no defined cause for their anaemia suggested a defect in both phosphotransferases. Here we report 10 patients with transfusion independent beta-thalassaemia; 8 being pure heterozygotes and 2 heterozygotes also for Hb E. Mean CDP-choline (86.xxx +/- 48 microM) and CDP-ethanolamine (34.6 microM +/- 34.5 microM), mean control <3 microM. Elevated CDP-choline in patients with no defined cause for their haemolytic anaemia was previously suggested as a possible indicator of CDP-choline phosphotransferase deficiency. Here we associate it with transfusion independent beta-thalassaemia.

High-dose therapy with hematopoietic transplantation for Hodgkin's lymphoma

The use of combination chemotherapy has been successful in treating advanced or widespread Hodgkin's disease (HD). For patients with relapsed disease, the long-term prognosis is much poorer, despite the good rate of reinduction into a second or further remission using conventional treatments. The majority of such patients will ultimately relapse again if given only conventional salvage chemotherapy. The transplantation or reinfusion of hematopoetic stem cells allows the use of higher doses of cytotoxic drugs that would normally be precluded by myelotoxicity. Hematopoiesis rescue by autologous transplantation of stem cells has become an accepted form of treatment for HD that has failed to respond to first-line chemotherapy, which has relapsed within 1 year after chemotherapy, or which has relapsed on more than one occasion. Dose escalation with autologous stem cells is fashionable, but there is an increasing tendency to consider allogeneic transplantation in HD. There may be some limited graft-versus-Hodgkin's lymphoma effect, but this is outweighed by the greatly increased treatment toxicity associated with the allogeneic procedure. It is possible, however, that modern low-intensity conditioning regimens, the so-called mini-allograft approach, may increase the use of allogeneic transplantation for poor-prognosis Hodgkin's lymphoma patients in the future.