[Show abstract][Hide abstract] ABSTRACT: The analysis of gene function in mature and activated natural killer cells has been hampered by the lack of model systems for Cre-mediated recombination in these cells. Here we have investigated the utility of GzmbCre for recombination of loxp sequences in these cells predicated on the observation that Gzmb mRNA is highly expressed in mature and activated natural killer cells. Using two different reporter strains we determined that gene function could be investigated in mature natural killer cells after GzmbCre mediated recombination in vitro in conditions that lead to natural killer cell activation such as in the cytokine combination of interleukin 2 and interleukin 12. We demonstrated the utility of this model by creating GzmbCre;Rosa26IKKbca mice in which Cre-mediated recombination resulted in expression of constitutively active IKKβ, which results in activation of the NFκB transcription factor. In vivo and in vitro activation of IKKβ in natural killer cells revealed that constitutive activation of this pathway leads to natural killer cell hyper-activation and altered morphology. As a caveat to the use of GzmbCre we found that this transgene can lead to recombination in all hematopoietic cells the extent of which varies with the particular loxp flanked allele under investigation. We conclude that GzmbCre can be used under some conditions to investigate gene function in mature and activated natural killer cells.
[Show abstract][Hide abstract] ABSTRACT: The immune system can be divided into innate and adaptive components that differ in their rate and mode of cellular activation, with innate immune cells being the first responders to invading pathogens. Recent advances in the identification and characterization of innate lymphoid cells have revealed reiterative developmental programs that result in cells with effector fates that parallel those of adaptive lymphoid cells and are tailored to effectively eliminate a broad spectrum of pathogenic challenges. However, activation of these cells can also be associated with pathologies such as autoimmune disease. One major distinction between innate and adaptive immune system cells is the constitutive expression of ID proteins in the former and inducible expression in the latter. ID proteins function as antagonists of the E protein transcription factors that play critical roles in lymphoid specification as well as B- and T-lymphocyte development. In this review, we examine the transcriptional mechanisms controlling the development of innate lymphocytes, including natural killer cells and the recently identified innate lymphoid cells (ILC1, ILC2, and ILC3), and innate-like lymphocytes, including natural killer T cells, with an emphasis on the known requirements for the ID proteins.
No preview · Article · Sep 2014 · Immunological Reviews
[Show abstract][Hide abstract] ABSTRACT: In this issue of Blood, Mallampati et al provide mechanistic insight into the functions of the transcription factor Sox4 in pro-B lymphocytes using both gain-of-function and loss-of-function approaches combined with global gene expression and genome-wide transcription factor binding analysis.
[Show abstract][Hide abstract] ABSTRACT: Invariant NKT (iNKT) cells display characteristics of both adaptive and innate lymphoid cells (ILCs). Like other ILCs, iNKT cells constitutively express ID proteins, which antagonize the E protein transcription factors that are essential for adaptive lymphocyte development. However, unlike ILCs, ID2 is not essential for thymic iNKT cell development. In this study, we demonstrated that ID2 and ID3 redundantly promoted iNKT cell lineage specification involving the induction of the signature transcription factor PLZF and that ID3 was critical for development of TBET-dependent NKT1 cells. In contrast, both ID2 and ID3 limited iNKT cell numbers by enforcing the postselection checkpoint in conventional thymocytes. Therefore, iNKT cells show both adaptive and innate-like requirements for ID proteins at distinct checkpoints during iNKT cell development.
Preview · Article · Nov 2013 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: The E2A transcription factors promote the development of thymus-seeding cells but it remains unknown whether these proteins play a role in T lymphocyte lineage specification or commitment. Here we showed that E2A proteins were required to promote T lymphocyte commitment from DN2 thymocytes and to extinguish their potential for alternative fates. E2A proteins functioned in DN2 cells to limit expression of Gata3, which encodes an essential T lymphocyte transcription factor whose ectopic expression can arrest T cell differentiation. Genetic, or siRNA-mediated, reduction of Gata3 rescued T cell differentiation in the absence of E2A and restricted the development of alternative lineages by limiting the expanded self-renewal potential in E2A(-/-) DN2 cells. Our data support a novel paradigm in lymphocyte lineage commitment in which the E2A proteins are necessary to limit the expression of an essential lineage specification and commitment factor in order to restrain self-renewal and prevent an arrest in differentiation.
[Show abstract][Hide abstract] ABSTRACT: Lineage commitment is regulated during hematopoiesis, with stepwise loss of differentiation potential ultimately resulting in lineage commitment. In this study we describe a novel population of B/NK bipotent precursors among common lymphoid progenitors in the fetal liver and the bone marrow. The absence of T cell precursor potential, both in vivo and in vitro, is due to low Notch1 expression and secondary to inhibition of E2A activity by members of the inhibitor of DNA binding (Id) protein family. Our results demonstrate a new, Id protein-dependent, molecular mechanism of Notch1 repression, operative in both fetal and adult common lymphoid progenitors, where T cell potential is selectively inhibited without affecting either the B or NK programs. This study identifies Id proteins as negative regulators of T cell specification, before B and NK commitment, and provides important insights into the transcriptional networks orchestrating hematopoiesis.
Preview · Article · Sep 2012 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Multiple transcription factors guide the development of mature functional natural killer (NK) cells, yet little is known about their function. We used global gene expression and genome-wide binding analyses combined with developmental and functional studies to unveil three roles for the ETS1 transcription factor in NK cells. ETS1 functions at the earliest stages of NK cell development to promote expression of critical transcriptional regulators including T-BET and ID2, NK cell receptors (NKRs) including NKp46, Ly49H, and Ly49D, and signaling molecules essential for NKR function. As a consequence, Ets1(-/-) NK cells fail to degranulate after stimulation through activating NKRs. Nonetheless, these cells are hyperresponsive to cytokines and have characteristics of chronic stimulation including increased expression of inhibitory NKRs and multiple activation-associated genes. Therefore, ETS1 regulates a broad gene expression program in NK cells that promotes target cell recognition while limiting cytokine-driven activation.
[Show abstract][Hide abstract] ABSTRACT: During B lymphopoiesis, recombination of the locus encoding the immunoglobulin κ-chain complex (Igk) requires expression of the precursor to the B cell antigen receptor (pre-BCR) and escape from signaling via the interleukin 7 receptor (IL-7R). By activating the transcription factor STAT5, IL-7R signaling maintains proliferation and represses Igk germline transcription by unknown mechanisms. We demonstrate that a STAT5 tetramer bound the Igk intronic enhancer (E(κi)), which led to recruitment of the histone methyltransferase Ezh2. Ezh2 marked trimethylation of histone H3 at Lys27 (H3K27me3) throughout the κ-chain joining region (J(κ)) to the κ-chain constant region (C(κ)). In the absence of Ezh2, IL-7 failed to repress Igk germline transcription. H3K27me3 modifications were lost after termination of IL-7R-STAT5 signaling, and the transcription factor E2A bound E(κi), which resulted in acquisition of H3K4me1 and acetylated histone H4 (H4Ac). Genome-wide analyses showed a STAT5 tetrameric binding motif associated with transcriptional repression. Our data demonstrate how IL-7R signaling represses Igk germline transcription and provide a general model for STAT5-mediated epigenetic transcriptional repression.
Full-text · Article · Dec 2011 · Nature Immunology
[Show abstract][Hide abstract] ABSTRACT: Recently in Cell, Novershtern et al. (2011) reported a comprehensive transcriptome analysis of human hematopoiesis, combined with sophisticated bioinformatics analysis and high-throughput DNA binding data for multiple transcription factors. The resulting map of regulatory interactions controlling stem cell differentiation provides a valuable resource for identification of novel hematopoietic regulators.
[Show abstract][Hide abstract] ABSTRACT: Loss of the transcription factor Ikaros is correlated with Notch receptor activation in T cell acute lymphoblastic leukemia (T-ALL). However, the mechanism remains unknown. We identified promoters in Notch1 that drove the expression of Notch1 proteins in the absence of a ligand. Ikaros bound to both canonical and alternative Notch1 promoters and its loss increased permissive chromatin, facilitating recruitment of transcription regulators. At early stages of leukemogenesis, increased basal expression from the canonical and 5'-alternative promoters initiated a feedback loop, augmenting Notch1 signaling. Ikaros also repressed intragenic promoters for ligand-independent Notch1 proteins that are cryptic in wild-type cells, poised in preleukemic cells, and active in leukemic cells. Only ligand-independent Notch1 isoforms were required for Ikaros-mediated leukemogenesis. Notch1 alternative-promoter usage was observed during T cell development and T-ALL progression. Thus, a network of epigenetic and transcriptional regulators controls conventional and unconventional Notch signaling during normal development and leukemogenesis.
[Show abstract][Hide abstract] ABSTRACT: Lymphopoiesis generates mature B, T, and NK lymphocytes from hematopoietic stem cells via a series of increasingly restricted developmental intermediates. The transcriptional networks that regulate these fate choices are composed of both common and lineage-specific components, which combine to create a cellular context that informs the developmental response to external signals. E proteins are an important factor during lymphopoiesis, and E2A in particular is required for normal T- and B-cell development. Although the other E proteins, HEB and E2-2, are expressed during lymphopoiesis and can compensate for some of E2A's activity, E2A proteins have non-redundant functions during early T-cell development and at multiple checkpoints throughout B lymphopoiesis. More recently, a role for E2A has been demonstrated in the generation of lymphoid-primed multipotent progenitors and shown to favor their specification toward lymphoid over myeloid lineages. This review summarizes both our current understanding of the wide-ranging functions of E proteins during the development of adaptive lymphocytes and the novel functions of E2A in orchestrating a lymphoid-biased cellular context in early multipotent progenitors.
Full-text · Article · Nov 2010 · Immunological Reviews
[Show abstract][Hide abstract] ABSTRACT: Hemokinin-1, encoded by the TAC4 gene, is a tachykinin most closely related to substance P. Previous studies have shown that TAC4 distinguishes itself from other tachykinins by its predominantly non-neuronal expression profile, particularly in cells of the immune system. Here we report for the first time that the highest levels of TAC4 expression are found in the olfactory epithelium. Furthermore, we identify olfactory neuron-specific transcription factor (Olf-1), also known as early B-cell factor (EBF), as a novel regulator of TAC4 expression. EBF present in the olfactory epithelium and in B cells binds to two sites in the TAC4 promoter and modulates expression in developing B cells. Our findings suggest a role for TAC4 in cell differentiation, and represent a regulatory bridge between the nervous system and the immune system.
No preview · Article · Oct 2010 · Journal of neuroimmunology
[Show abstract][Hide abstract] ABSTRACT: The TLX1 oncogene (encoding the transcription factor T cell leukemia homeobox protein-1) has a major role in the pathogenesis of T cell acute lymphoblastic leukemia (T-ALL). However, the specific mechanisms of T cell transformation downstream of TLX1 remain to be elucidated. Here we show that transgenic expression of human TLX1 in mice induces T-ALL with frequent deletions and mutations in Bcl11b (encoding B cell leukemia/lymphoma-11B) and identify the presence of recurrent mutations and deletions in BCL11B in 16% of human T-ALLs. Most notably, mouse TLX1 tumors were typically aneuploid and showed a marked defect in the activation of the mitotic checkpoint. Mechanistically, TLX1 directly downregulates the expression of CHEK1 (encoding CHK1 checkpoint homolog) and additional mitotic control genes and induces loss of the mitotic checkpoint in nontransformed preleukemic thymocytes. These results identify a previously unrecognized mechanism contributing to chromosomal missegregation and aneuploidy active at the earliest stages of tumor development in the pathogenesis of cancer.