The transcription factor Interferon Regulatory Factor 4 is required for the generation of protective effector CD8+ T cells.

Robust cytotoxic CD8(+) T-cell response is important for immunity to intracellular pathogens. Here, we show that the transcription factor IFN Regulatory Factor 4 (IRF4) is crucial for the protective CD8(+) T-cell response to the intracellular bacterium Listeria monocytogenes. IRF4-deficient (Irf4(-/-)) mice could not clear L. monocytogenes infection and generated decreased numbers of L. monocytogenes-specific CD8(+) T cells with impaired effector phenotype and function. Transfer of wild-type CD8(+) T cells into Irf4(-/-) mice improved bacterial clearance, suggesting an intrinsic defect of CD8(+) T cells in Irf4(-/-) mice. Following transfer into wild-type recipients, Irf4(-/-) CD8(+) T cells became activated and showed initial proliferation upon L. monocytogenes infection. However, these cells could not sustain proliferation, produced reduced amounts of IFN-γ and TNF-α, and failed to acquire cytotoxic function. Forced IRF4 expression in Irf4(-/-) CD8(+) T cells rescued the defect. During acute infection, Irf4(-/-) CD8(+) T cells demonstrated diminished expression of B lymphocyte-induced maturation protein-1 (Blimp-1), inhibitor of DNA binding (Id)2, and T-box expressed in T cells (T-bet), transcription factors programming effector-cell generation. IRF4 was essential for expression of Blimp-1, suggesting that altered regulation of Blimp-1 contributes to the defects of Irf4(-/-) CD8(+) T cells. Despite increased levels of B-cell lymphoma 6 (BCL-6), Eomesodermin, and Id3, Irf4(-/-) CD8(+) T cells showed impaired memory-cell formation, indicating additional functions for IRF4 in this process. As IRF4 governs B-cell and CD4(+) T-cell differentiation, the identification of its decisive role in peripheral CD8(+) T-cell differentiation, suggests a common regulatory function for IRF4 in adaptive lymphocytes fate decision.

Epigenetic Regulation in Early Childhood: A Miniaturized and Validated Method to Assess Histone Acetylation.

INTRODUCTION: Chronic inflammatory diseases including allergies and asthma are the result of complex interactions between genes and environmental factors. Epigenetic mechanisms comprise a set of biochemical reactions that regulate gene expression. In order to understand the cause-effect relationship between environmental exposures and disease development, methods capable of assessing epigenetic regulation (also) in large cohorts are needed. METHODS: For this purpose, we developed and evaluated a miniaturized chromatin immunoprecipitation (ChIP) assay allowing for a cost-effective assessment of histone acetylation of candidate genes in a quantitative fashion. This method was then applied to assess H3 and H4 histone acetylation changes in cord blood (CB) samples from an established cohort of Australian children exposed in the fetal period to either very low or very high levels of maternal folate. RESULTS: Our ChIP assay was validated for a minimum requirement of 1 × 105 target cells (e.g. CD4+ T cells). Very high levels of maternal folate were significantly associated with increased H3/H4 acetylation at GATA3 and/or IL9 promoter regions in CD4+ T cells in CB. CONCLUSION: We developed a ChIP method allowing reliable assessment of H3/H4 acetylation using 1 × 105 cells only. Practical application of this assay demonstrated an association between high maternal folate exposure and increased histone acetylation, corresponding to a more transcriptionally permissive chromatin status in the promoter regions of some Th2-related genes.

Regulation of Calvarial Osteogenesis by Concomitant De-repression of GLI3 and Activation of IHH Targets.

Loss-of-function mutations in GLI3 and IHH cause craniosynostosis and reduced osteogenesis, respectively. In this study, we show that Ihh ligand, the receptor Ptch1 and Gli transcription factors are differentially expressed in embryonic mouse calvaria osteogenic condensations. We show that in both Ihh-/- and Gli3Xt-J/Xt-J embryonic mice, the normal gene expression architecture is lost and this results in disorganized calvarial bone development. RUNX2 is a master regulatory transcription factor controlling osteogenesis. In the absence of Gli3, RUNX2 isoform II and IHH are upregulated, and RUNX2 isoform I downregulated. This is consistent with the expanded and aberrant osteogenesis observed in Gli3Xt-J/Xt-J mice, and consistent with Runx2-I expression by relatively immature osteoprogenitors. Ihh-/- mice exhibited small calvarial bones and HH target genes, Ptch1 and Gli1, were absent. This indicates that IHH is the functional HH ligand, and that it is not compensated by another HH ligand. To decipher the roles and potential interaction of Gli3 and Ihh, we generated Ihh-/-;Gli3Xt-J/Xt-J compound mutant mice. Even in the absence of Ihh, Gli3 deletion was sufficient to induce aberrant precocious ossification across the developing suture, indicating that the craniosynostosis phenotype of Gli3Xt-J/Xt-J mice is not dependent on IHH ligand. Also, we found that Ihh was not required for Runx2 expression as the expression of RUNX2 target genes was unaffected by deletion of Ihh. To test whether RUNX2 has a role upstream of IHH, we performed RUNX2 siRNA knock down experiments in WT calvarial osteoblasts and explants and found that Ihh expression is suppressed. Our results show that IHH is the functional HH ligand in the embryonic mouse calvaria osteogenic condensations, where it regulates the progression of osteoblastic differentiation. As GLI3 represses the expression of Runx2-II and Ihh, and also elevates the Runx2-I expression, and as IHH may be regulated by RUNX2 these results raise the possibility of a regulatory feedback circuit to control calvarial osteogenesis and suture patency. Taken together, RUNX2-controlled osteoblastic cell fate is regulated by IHH through concomitant inhibition of GLI3-repressor formation and activation of downstream targets.

The role of PKCζ in cord blood T-cell maturation towards Th1 cytokine profile and its epigenetic regulation by fish oil.

While immunodeficiency of immaturity of the neonate has been considered important as the basis for unusual susceptibility to infection, it has also been recognized that the ability to progress from an immature Th2 cytokine predominance to a Th1 profile has relevance in determining whether children will develop allergy, providing an opportunity for epigenetic regulation through environmental pressures. However, this notion remains relatively unexplored. Here, we present evidence that there are two major control points to explain the immunodeficiency in cord blood (CB) T-cells, a deficiency in interleukin (IL)-12 (IL-12) producing and IL-10 overproducing accessory cells, leading to a decreased interferon γ (IFNγ) synthesis and the other, an intrinsic defect in T-cell protein kinase C (PKC) ζ (PKCζ) expression. An important finding was that human CB T-cells rendered deficient in PKCζ, by shRNA knockdown, develop into low tumour necrosis factor α (TNFα) and IFNγ but increased IL-13 producing cells. Interestingly, we found that the increase in PKCζ levels in CB T-cells caused by prenatal supplementation with fish oil correlated with modifications of histone acetylation at the PKCζ gene (PRKCZ) promoter. The data demonstrate that PKCζ expression regulates the maturation of neonatal T-cells into specific functional phenotypes and that environmental influences may work via PKCζ to regulate these phenotypes and disease susceptibility.

Draft Genome Sequence and Complete Plasmid Sequence of Acinetobacter lwoffii F78, an Isolate with Strong Allergy-Protective Properties.

The hygiene hypothesis states that the tremendous increase in atopic diseases correlates significantly with less contact to microbes in childhood. Here, we report the draft genome sequence of Acinetobacter lwoffii F78, a rural cowshed isolate with strong allergy-protective properties that contains an 8,579-bp plasmid.

Epigenetics in immune development and in allergic and autoimmune diseases.

Epigenetic mechanisms such as DNA methylation, histone modification, and micro RNA signaling regulate the activity of the genome. Virtually all aspects of immunity involve some level of epigenetic regulation, whether it be host defense or in mediating tolerance. These processes are critically important in mediating dynamic responses to the environment over the life course of the individual, yet we are only just beginning to understand how dysregulation in these pathways may play a role in immune disease. Here, we give a brief chronological overview of epigenetic processes during immune development in health and disease.

Loss-of-Function of Gli3 in Mice Causes Abnormal Frontal Bone Morphology and Premature Synostosis of the Interfrontal Suture.

Greig cephalopolysyndactyly syndrome (GCPS) is an autosomal dominant disorder with polydactyly and syndactyly of the limbs and a broad spectrum of craniofacial abnormalities. Craniosynostosis of the metopic suture (interfrontal suture in mice) is an important but rare feature associated with GCPS. GCPS is caused by mutations in the transcription factor GLI3, which regulates Hedgehog signaling. The Gli3 loss-of-function (Gli3(Xt-J/Xt-J)) mouse largely phenocopies the human syndrome with the mice exhibiting polydactyly and several craniofacial abnormalities. Here we show that Gli3(Xt-J/Xt-J) mice exhibit ectopic ossification in the interfrontal suture and in the most severe cases the suture fuses already prior to birth. We show that abnormalities in frontal bones occur early in calvarial development, before the establishment of the interfrontal suture. It provides a model for the metopic suture pathology that can occur in GCPS.

WASP and SCAR have distinct roles in activating the Arp2/3 complex during myoblast fusion.

Myoblast fusion takes place in two steps in mammals and in Drosophila. First, founder cells (FCs) and fusion-competent myoblasts (FCMs) fuse to form a trinucleated precursor, which then recruits further FCMs. This process depends on the formation of the fusion-restricted myogenic-adhesive structure (FuRMAS), which contains filamentous actin (F-actin) plugs at the sites of cell contact. Fusion relies on the HEM2 (NAP1) homolog Kette, as well as Blow and WASP, a member of the Wiskott-Aldrich-syndrome protein family. Here, we show the identification and characterization of schwächling--a new Arp3-null allele. Ultrastructural analyses demonstrate that Arp3 schwächling mutants can form a fusion pore, but fail to integrate the fusing FCM. Double-mutant experiments revealed that fusion is blocked completely in Arp3 and wasp double mutants, suggesting the involvement of a further F-actin regulator. Indeed, double-mutant analyses with scar/WAVE and with the WASP-interacting partner vrp1 (sltr, wip)/WIP show that the F-actin regulator scar also controls F-actin formation during myoblast fusion. Furthermore, the synergistic phenotype observed in Arp3 wasp and in scar vrp1 double mutants suggests that WASP and SCAR have distinct roles in controlling F-actin formation. From these findings we derived a new model for actin regulation during myoblast fusion.